Invasive sense measurement in prosthesis installation

ABSTRACT

A system and method for allowing any surgeon, including those surgeons who perform a fewer number of a replacement procedure as compared to a more experienced surgeon who performs a greater number of procedures, to provide an improved likelihood of a favorable outcome approaching, if not exceeding, a likelihood of a favorable outcome as performed by a very experienced surgeon with the replacement procedure. Force sensing is included to aid in quantifying installation of an implant, particularly a cup into a pelvic bone.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 15/284,091filed on Oct. 3, 2016, application Ser. No. 15/284,091 is aContinuation-in-part of application Ser. No. 15/234,782 filed on Aug.11, 2016, application Ser. No. 15/234,782 is a Continuation-in-part ofapplication Ser. No. 15/202,434 filed on Jul. 5, 2016, Application Ser.No. 15/202,434 claims the benefit of U.S. Provisional Application62/277,294 filed on Jan. 11, 2016, application Ser. No. 15/234,782claims the benefit of U.S. Provisional Application 62/355,657 filed onJun. 28, 2016, application Ser. No. 15/234,782 claims the benefit ofU.S. Provisional Application 62/353,024 filed on Jun. 21, 2016, thecontents of each of these applications in their entireties are herebyexpressly incorporated by reference thereto for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to orthopedic surgical systemsand procedures employing a prosthetic implant for, and morespecifically, but not exclusively, to joint replacement therapies suchas total hip replacement including controlled installation andpositioning of the prosthesis such as during replacement of a pelvicacetabulum with a prosthetic implant, and relates generally toinstallation of a prosthesis, and more specifically, but notexclusively, to improvements in prosthesis placement and positioning,and relates generally to force measurement systems such as may be usedin these systems and methods.

BACKGROUND OF THE INVENTION

The subject matter discussed in the background section should not beassumed to be prior art merely as a result of its mention in thebackground section. Similarly, a problem mentioned in the backgroundsection or associated with the subject matter of the background sectionshould not be assumed to have been previously recognized in the priorart. The subject matter in the background section merely representsdifferent approaches, which in and of themselves may also be inventions.

Total hip replacement refers to a surgical procedure where a hip jointis replaced using a prosthetic implant. There are several differenttechniques that may be used, but all include a step of inserting anacetabular component into the acetabulum and positioning it correctly inthree dimensions (along an X, Y, and Z axis).

In total hip replacement (THR) procedures there are advantages topatient outcome when the procedure is performed by a surgeonspecializing in these procedures. Patients of surgeons who do notperform as many procedures can have increased risks of complications,particularly of complications arising from incorrect placement andpositioning of the acetabular component.

The incorrect placement and positioning may arise even when the surgeonunderstood and intended the acetabular component to be inserted andpositioned correctly. This is true because in some techniques, the toolsfor actually installing the acetabular component are crude and providean imprecise, unpredictable coarse positioning outcome.

It is known in some techniques to employ automated and/orcomputer-assisted navigation tools, for example, x-ray fluoroscopy orcomputer guidance systems. There are computer assisted surgerytechniques that can help the surgeon in determining the correctorientation and placement of the acetabular component. However, currenttechnology provides that at some point the surgeon is required to employa hammer/mallet to physically strike a pin or alignment rod. The amountof force applied and the location of the application of the force arevariables that have not been controlled by these navigation tools. Thus,even when the acetabular component is properly positioned and oriented,when actually impacting the acetabular component into place the actuallocation and orientation can differ from the intended optimum locationand orientation. In some cases, the tools used can be used to determinethat there is, in fact, some difference in the location and/ororientation. However, once again the surgeon must employ an impactingtool (e.g., the hammer/mallet) to strike the pin or alignment rod toattempt an adjustment. However, the resulting location and orientationof the acetabular component after the adjustment may not be, in fact,the desired location and/or orientation. The more familiar that thesurgeon is with the use and application of these adjustment tools canreduce the risk to a patient from a less preferred location ororientation. In some circumstances, quite large impacting forces areapplied to the prosthesis by the mallet striking the rod; these forcesmake fine tuning difficult at best and there is risk of fracturingand/or shattering the acetabulum during these impacting steps.

Earlier patents issued to the present applicant have described problemsassociated with prosthesis installation, for example acetabular cupplacement in total hip replacement surgery. See U.S. Pat. Nos. 9,168,154and 9,220,612, which are hereby expressly incorporated by referencethereto in their entireties for all purposes. Even though hipreplacement surgery has been one of the most successful operations, itcontinues to be plagued with a problem of inconsistent acetabular cupplacement. Cup mal-positioning is the single greatest cause of hipinstability, a major factor in polyethylene wear, osteolysis,impingement, component loosening and the need for hip revision surgery.

These incorporated patents explain that the process of cup implantationwith a mallet is highly unreliable and a significant cause of thisinconsistency. The patents note two specific problems associated withthe use of the mallet. First is the fact that the surgeon is unable toconsistently hit on the center point of the impaction plate, whichcauses undesirable torques and moment arms, leading to mal-alignment ofthe cup. Second, is the fact that the amount of force utilized in thisprocess is non-standardized.

Traditionally these methods do not have any clear understanding of theforces, including magnitude and direction, involved in installing aprosthesis. A surgeon often relies on qualitative factors from tactileand auditory senses. Consequently, the surgeon is left somewhathaphazardly and variably relying on two different fixation methods(e.g., pins and press-fit) without knowing how or why.

In these patents there is presented a new apparatus and method of cupinsertion which uses an oscillatory motion to insert the prosthesis.Prototypes have been developed and continue to be refined, andillustrate that vibratory force may allow insertion of the prosthesiswith less force, as well, in some embodiments, of allowing simultaneouspositioning and alignment of the implant.

There are other ways of breaking down of the large undesirable,torque-producing forces associated with the discrete blows of the malletinto a series of smaller, axially aligned controlled taps, which mayachieve the same result incrementally, and in a stepwise fashion tothose set forth in the incorporated patents, (with regard to, forexample, cup insertion without unintended divergence).

There are two problems that may be considered independently, though somesolutions may address both in a single solution. These problems includei) undesirable and unpredictable torques and moment arms that arerelated to the primitive method currently used by surgeons, whichinvolves manually banging the mallet on an impaction plate mated to theprosthesis and ii) non-standardized and essentially uncontrolled andunquantized amounts of force utilized in these processes.

Total hip replacement has been one of the most successful orthopedicoperations. However, as has been previously described in theincorporated applications, it continues to be plagued with the problemof inconsistent acetabular cup placement. Cup mal-positioning is asignificant cause of hip instability, a major factor in polyethylenewear, osteolysis, impingement, component loosening, and the need for hiprevision surgery.

Solutions in the incorporated applications generally relate toparticular solutions that may not, in every situation andimplementation, achieve desired goal(s) of a surgeon.

There are various sensing systems that may be used over a course ofpreparation and installation of a prosthesis, for example an acetabularcup. These sensing systems may detect various parameters such as anorientation angle of the prosthesis at any given time. These sensingsystems may provide a set of periodic snapshots in time over the courseof the procedure, but they do not provide true real-time continuous dataover the installation procedure. That is, a surgeon may employ a sensingsystem to measure an orientation before striking an acetabular cup usinga mallet and tamp, and may employ a sensing system to measure anorientation after striking the acetabular cup. But these sensing systemsdo not provide an orientation measurement (and in most cases nomeasurement of any information) during the strike. That is, the surgeonoften measures, strikes, remeasures, restrikes, and repeats until thesurgeon decides to stop. For a conventional system in which the surgeonmanually swings the mallet and the installation model includes asequence of discrete impulses from the mallet, this paradigm isunderstandable.

Some conventional systems may describe some measurements as “real time”but those systems are real time in the sense that the measurements aretaken in the operating room during a procedure. The actual system doesnot provide real-time measurement during the actual insertion event.

In the incorporated applications, alternatives to the manual swinging ofthe mallet are described and in these systems the conventionalmeasurement paradigm may be unnecessarily restrictive.

What is needed is a system and method for allowing any surgeon,including those surgeons who perform a fewer number of a replacementprocedure as compared to a more experienced surgeon who performs agreater number of procedures, to provide an improved likelihood of afavorable outcome approaching, if not exceeding, a likelihood of afavorable outcome as performed by a very experienced surgeon with thereplacement procedure, such as by understanding the prosthesisinstallation environment (e.g., cup/cavity interface) and to provideintelligent and interactive tools and methods to standardize theinstallation process.

BRIEF SUMMARY OF THE INVENTION

Disclosed is a system and method for allowing any surgeon, includingthose surgeons who perform a fewer number of a replacement procedure ascompared to a more experienced surgeon who performs a greater number ofprocedures, to provide an improved likelihood of a favorable outcomeapproaching, if not exceeding, a likelihood of a favorable outcome asperformed by a very experienced surgeon with the replacement procedure,such as by understanding the prosthesis installation environment (e.g.,cup/cavity interface) and to provide intelligent and interactive toolsand methods to standardize the installation process.

The following summary of the invention is provided to facilitate anunderstanding of some of technical features related to total hipreplacement, and is not intended to be a full description of the presentinvention. A full appreciation of the various aspects of the inventioncan be gained by taking the entire specification, claims, drawings, andabstract as a whole. The present invention is applicable to othersurgical procedures, including replacement of other joints replaced by aprosthetic implant in addition to replacement of an acetabulum (hipsocket) with an acetabular component (e.g., a cup). Use of pneumatic andelectric motor implementations have both achieved a proof of conceptdevelopment.

The disclosed concepts involve creation of a system/method/tool/gun thatvibrates an attached prosthesis, e.g., an acetabular cup. The gun wouldbe held in a surgeon's hands and deployed. It would use a vibratoryenergy to insert (not impact) and position the cup into desiredalignment (using current intra-operation measurement systems,navigation, fluoroscopy, and the like).

In one embodiment, a first gun-like device is used for accurateimpaction of the acetabular component at the desired location andorientation.

In another embodiment, a second gun-like device is used for fine-tuningof the orientation of the acetabular component, such as one installed bythe first gun-like device, by traditional mallet and tamp, or by othermethodology. However, the second gun-like device may be usedindependently of the first gun-like device for adjusting an acetabularcomponent installed using an alternate technique. Similarly, the secondgun-like device may be used independently of the first gun-like device,particularly when the initial installation is sufficiently close to thedesired location and orientation. These embodiments are not necessarilylimited to fine-tuning as certain embodiments permit completere-orientation. Some implementations allow for removal of an installedprosthesis.

Another embodiment includes a third gun-like device that combines thefunctions of the first gun-like device and the second gun-like device.This embodiment enables the surgeon to accurately locate, insert,orient, and otherwise position the acetabular component with the singletool.

Another embodiment includes a fourth device that installs the acetabularcomponent without use of the mallet and the rod, or use of alternativesto strike the acetabular component for impacting it into the acetabulum.This embodiment imparts a vibratory motion to an installation rodcoupled to the acetabular component that enables low-force, impactlessinstallation and/or positioning.

An embodiment of the present invention may include axial alignment offorce transference, such as, for example, an axially sliding hammermoving between stops to impart a non-torqueing installation force. Thereare various ways of motivating and controlling the sliding hammer,including a magnitude of transferred force. Optional enhancements mayinclude pressure and/or sound sensors for gauging when a desired depthof implantation has occurred.

Other embodiments include adaptation of various devices for accurateassembly of modular prostheses, such as those that include a headaccurately impacted onto a trunnion taper that is part of a stem orother element of the prosthesis.

Additional embodiments of the present invention may include a hybridmedical device that is capable of selectively using vibratory and/oraxial-impacts at various phases of an installation as required, needed,and/or desired by the surgeon during a procedure. The single toolremains coupled to the prosthesis or prosthesis component as the surgeonoperates the hybrid medical device in any of its phases, which include apure vibratory mode, a pure axial mode, a blended vibratory andimpactful mode. The axial impacts in this device may have sub-modes: a)unidirectional axial force-IN, b) unidirectional axial force-OUT, or c)bidirectional axial force.

An embodiment of the present invention may include true real-timesensing before, during, and after a procedure. These procedures maybenefit from this invasive sensing (sensing during preparation of bone,during installation of a prosthesis, and during assembly of a modularprosthesis) and not just periodic static snapshots. The invasive sensingmay employ force sensing directly, or may employ acceleration,vibration, or acoustic sensing in addition to, or in lieu of, forcesensing.

A positioning device for an acetabular cup disposed in a bone, theacetabular cup including an outer shell having a sidewall defining aninner cavity and an opening with the sidewall having a periphery aroundthe opening and with the acetabular cup having a desired abduction anglerelative to the bone and a desired anteversion angle relative to thebone, including a controller including a trigger and a selector; asupport having a proximal end and a distal end opposite of the proximalend, the support further having a longitudinal axis extending from theproximal end to the distal end with the proximal end coupled to thecontroller, the support further having an adapter coupled to the distalend with the adapter configured to secure the acetabular cup; and anumber N, the number N, an integer greater than or equal to 2, oflongitudinal actuators coupled to the controller and disposed around thesupport generally parallel to the longitudinal axis, each the actuatorincluding an associated impact head arranged to strike a portion of theperiphery, each impact head providing an impact strike to a differentportion of the periphery when the associated actuator is selected andtriggered; wherein each the impact strike adjusts one of the anglesrelative to the bone.

An installation device for an acetabular cup disposed in a pelvic bone,the acetabular cup including an outer shell having a sidewall definingan inner cavity and an opening with the sidewall having a peripheryaround the opening and with the acetabular cup having a desiredinstallation depth relative to the bone, a desired abduction anglerelative to the bone, and a desired anteversion angle relative to thebone, including a controller including a trigger; a support having aproximal end and a distal end opposite of said proximal end, saidsupport further having a longitudinal axis extending from said proximalend to said distal end with said proximal end coupled to saidcontroller, said support further having an adapter coupled to saiddistal end with said adapter configured to secure the acetabular cup;and an oscillator coupled to said controller and to said support, saidoscillator configured to control an oscillation frequency and anoscillation magnitude of said support with said oscillation frequencyand said oscillation magnitude configured to install the acetabular cupat the installation depth with the desired abduction angle and thedesired anteversion angle without use of an impact force applied to theacetabular cup.

An installation system for a prosthesis configured to be implanted intoa portion of bone at a desired implantation depth, the prosthesisincluding an attachment system, including an oscillation engineincluding a controller coupled to a vibratory machine generating anoriginal series of pulses having a generation pattern, said generationpattern defining a first duty cycle of said original series of pulses;and a pulse transfer assembly having a proximal end coupled to saidoscillation engine and a distal end, spaced from said proximal end,coupled to the prosthesis with said pulse transfer assembly including aconnector system at said proximal end, said connector systemcomplementary to the attachment system and configured to secure andrigidly hold the prosthesis producing a secured prosthesis with saidpulse transfer assembly communicating an installation series of pulses,responsive to said original series of pulses, to said secured prosthesisproducing an applied series of pulses responsive to said installationseries of pulses; wherein said applied series of pulses are configuredto impart a vibratory motion to said secured prosthesis enabling aninstallation of said secured prosthesis into the portion of bone towithin 95% of the desired implantation depth without a manual impact.

A method for installing an acetabular cup into a prepared socket in apelvic bone, the acetabular cup including an outer shell having asidewall defining an inner cavity and an opening with the sidewallhaving a periphery around the opening and with the acetabular cup havinga desired installation depth relative to the bone, a desired abductionangle relative to the bone, and a desired anteversion angle relative tothe bone, including (a) generating an original series of pulses from anoscillation engine; (b) communicating said original series of pulses tothe acetabular cup producing a communicated series of pulses at saidacetabular cup; (c) vibrating, responsive to said communicated series ofpulses, the acetabular cup to produce a vibrating acetabular cup havinga predetermined vibration pattern; and (d) inserting the vibratingacetabular cup into the prepared socket within a first predefinedthreshold of the installation depth with the desired abduction angle andthe desired anteversion angle without use of an impact force applied tothe acetabular cup.

This method may further include (e) orienting the vibrating acetabularcup within the prepared socket within a second predetermined thresholdof the desired abduction angle and within third predetermined thresholdof the desired anteversion angle.

A method for inserting a prosthesis into a prepared location in a boneof a patient at a desired insertion depth wherein non-vibratoryinsertion forces for inserting the prosthesis to the desired insertiondepth are in a first range, the method including (a) vibrating theprosthesis using a tool to produce a vibrating prosthesis having apredetermined vibration pattern; and (b) inserting the vibratingprosthesis into the prepared location to within a first predeterminedthreshold of the desired insertion depth using vibratory insertionforces in a second range, said second range including a set of valuesless than a lowest value of the first range.

An embodiment may include a force sensing system within the BMD toolswith capacity to measure the force experienced by the system (mIF)(Within the tool) and calculate the change in mIF with respect to time,number of impacts, or depth of insertion. This system provides afeedback mechanism through the BMD tools, for the surgeon, as to whenimpaction should stop, and or if it should continue. This feedbackmechanism can be created by measuring and calculating force,acceleration or insertion depth. In some implementations, an appliedforce is measured (TmIF) and compared against the mIF in any of severalpossible ways and an evaluation is made as to whether the prosthesis hasstopped moving responsive to the applied forces. There are differentimplications depending upon where in the installation process the systemis operating. In other implementations, the applied force is known orestimated and then the mIF may need to be measured.

An aspect of the present invention is use of a special version of thissystem to map out ranges of parameters for different prosthesis/cavityinteractions to allow better understanding of typical or applicablecurve for a particular patient with a particular implant procedure.

A force sensing system for a medical device tools with capacity tomeasure the force experienced by the system (mIF)—(Within the tool) andcalculate a change in mIF with respect to time, number of impacts, ordepth of insertion, wherein this system provides a feedback mechanismthrough the device, for the surgeon, as to when impaction should stop,and/or whether it should continue while assessing a risk of too earlysuspension with poor seating or too late when bone fracture risk is highand wherein this feedback mechanism can be created by measuring andcalculating force, acceleration or insertion depth, among othervariables.

An apparatus, including a medical device operating over a continuousperiod including an initial act with the medical device to a subsequentact with the medical device; and a microelectromechanical (MEM) sensingsystem physically coupled to the medical device configured to provide areal-time parametric evaluation over the period.

Any of the embodiments described herein may be used alone or togetherwith one another in any combination. Inventions encompassed within thisspecification may also include embodiments that are only partiallymentioned or alluded to or are not mentioned or alluded to at all inthis brief summary or in the abstract. Although various embodiments ofthe invention may have been motivated by various deficiencies with theprior art, which may be discussed or alluded to in one or more places inthe specification, the embodiments of the invention do not necessarilyaddress any of these deficiencies. In other words, different embodimentsof the invention may address different deficiencies that may bediscussed in the specification. Some embodiments may only partiallyaddress some deficiencies or just one deficiency that may be discussedin the specification, and some embodiments may not address any of thesedeficiencies.

Other features, benefits, and advantages of the present invention willbe apparent upon a review of the present disclosure, including thespecification, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, in which like reference numerals refer toidentical or functionally-similar elements throughout the separate viewsand which are incorporated in and form a part of the specification,further illustrate the present invention and, together with the detaileddescription of the invention, serve to explain the principles of thepresent invention.

FIG. 1 illustrates a set of “cup prints” for a number of interactionsbetween a cup and a cavity;

FIG. 2 illustrates a particular one representative cup print;

FIG. 3 illustrates a controlled modulated installation force envelope;

FIG. 4 illustrates an example installation force envelope that isrepresentative of use of a mallet in its production;

FIG. 5 illustrates an example installation force envelope that isrepresentative of use of a BMD3 in its production;

FIG. 6 illustrates an example installation force envelope that isrepresentative of use of a BMD4 in its production;

FIG. 7-FIG. 10 relate to a vibratory Behzadi Medical Device (BMD3);

FIG. 7 illustrates a representative installation system;

FIG. 8 illustrates a disassembly of the representative installationsystem of FIG. 7;

FIG. 9 illustrates a first disassembly view of the pulse transferassembly of the installation system of FIG. 7;

FIG. 10 illustrates a second disassembly view of the pulse transferassembly of the installation system of FIG. 7;

FIG. 11 illustrates an embodiment for a sliding impact device having apressure sensor to provide feedback and attachment of an optionalnavigation device;

FIG. 12 illustrates a Force Resistance (FR) curve;

FIG. 13-FIG. 14 illustrate a general force measurement system forunderstanding an installation of a prosthesis into an installation site(e.g., an acetabular cup into an acetabulum during total hip replacementprocedures);

FIG. 13 illustrates an initial engagement of a prosthesis to a cavitywhen the prosthesis is secured to a force sensing tool;

FIG. 14 illustrates a partial installation of the prosthesis of FIG. 13into the cavity by operation of the force sensing tool;

FIG. 15 illustrates a generalized FR curve illustrating variousapplicable forces implicated in operation of the tool in FIG. 13 andFIG. 14;

FIG. 16-FIG. 21 illustrate a first specific implementation of the systemand method of FIG. 13-FIG. 15;

FIG. 16 illustrates a representative plot of insertion force for a cupduring installation;

FIG. 17 illustrates a first particular embodiment of a BMDX forcesensing tool;

FIG. 18 illustrates a graph including results of a drop test over time;

FIG. 19 illustrates a graph of measured impact force as impact energy isincreased;

FIG. 20 illustrates a discrete impact control and measurement process;and

FIG. 21 illustrates a warning process; and

FIG. 22-FIG. 27 illustrate a second specific implementation of thesystem and method of FIG. 13-FIG. 15;

FIG. 22 illustrates a basic force sensor system for controlledinsertion;

FIG. 23 illustrates an FR curve including TmIF and mIF as functions ofdisplacement;

FIG. 24 illustrates a generic force sensor tool to access variables ofinterest in FIG. 23;

FIG. 25 illustrates a B-cloud tracking process using TmIF and MIFmeasurements;

FIG. 26 illustrates a control system for the “controlled action”referenced in FIG. 25;

FIG. 27 illustrates possible B-cloud regulation strategies; and

FIG. 28 illustrates a generalized BMD including real-time invasive sensemeasurement.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide a system and method forallowing any surgeon, including those surgeons who perform a fewernumber of a replacement procedure as compared to a more experiencedsurgeon who performs a greater number of procedures, to provide animproved likelihood of a favorable outcome approaching, if notexceeding, a likelihood of a favorable outcome as performed by a veryexperienced surgeon with the replacement procedure, such as byunderstanding the prosthesis installation environment (e.g., cup/cavityinterface) and to provide intelligent and interactive tools and methodsto standardize the installation process. The following description ispresented to enable one of ordinary skill in the art to make and use theinvention and is provided in the context of a patent application and itsrequirements.

Various modifications to the preferred embodiment and the genericprinciples and features described herein will be readily apparent tothose skilled in the art. Thus, the present invention is not intended tobe limited to the embodiment shown but is to be accorded the widestscope consistent with the principles and features described herein.

Definitions

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this general inventive conceptbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand the present disclosure, and will not be interpreted in an idealizedor overly formal sense unless expressly so defined herein.

The following definitions apply to some of the aspects described withrespect to some embodiments of the invention. These definitions maylikewise be expanded upon herein.

As used herein, the term “or” includes “and/or” and the term “and/or”includes any and all combinations of one or more of the associatedlisted items. Expressions such as “at least one of,” when preceding alist of elements, modify the entire list of elements and do not modifythe individual elements of the list.

As used herein, the singular terms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to an object can include multiple objects unless thecontext clearly dictates otherwise.

Also, as used in the description herein and throughout the claims thatfollow, the meaning of “in” includes “in” and “on” unless the contextclearly dictates otherwise. It will be understood that when an elementis referred to as being “on” another element, it can be directly on theother element or intervening elements may be present therebetween. Incontrast, when an element is referred to as being “directly on” anotherelement, there are no intervening elements present.

As used herein, the term “set” refers to a collection of one or moreobjects. Thus, for example, a set of objects can include a single objector multiple objects. Objects of a set also can be referred to as membersof the set. Objects of a set can be the same or different. In someinstances, objects of a set can share one or more common properties.

As used herein, the term “adjacent” refers to being near or adjoining.Adjacent objects can be spaced apart from one another or can be inactual or direct contact with one another. In some instances, adjacentobjects can be coupled to one another or can be formed integrally withone another.

As used herein, the terms “connect,” “connected,” and “connecting” referto a direct attachment or link. Connected objects have no or nosubstantial intermediary object or set of objects, as the contextindicates.

As used herein, the terms “couple,” “coupled,” and “coupling” refer toan operational connection or linking. Coupled objects can be directlyconnected to one another or can be indirectly connected to one another,such as via an intermediary set of objects.

As used herein, the terms “substantially” and “substantial” refer to aconsiderable degree or extent. When used in conjunction with an event orcircumstance, the terms can refer to instances in which the event orcircumstance occurs precisely as well as instances in which the event orcircumstance occurs to a close approximation, such as accounting fortypical tolerance levels or variability of the embodiments describedherein.

As used herein, the terms “optional” and “optionally” mean that thesubsequently described event or circumstance may or may not occur andthat the description includes instances where the event or circumstanceoccurs and instances in which it does not.

As used herein, the term “bone” means rigid connective tissue thatconstitute part of a vertebral skeleton, including mineralized osseoustissue, particularly in the context of a living patient undergoing aprosthesis implant into a portion of cortical bone. A living patient,and a surgeon for the patient, both have significant interests inreducing attendant risks of conventional implanting techniques includingfracturing/shattering the bone and improper installation and positioningof the prosthesis within the framework of the patient's skeletal systemand operation.

As used herein, the term “size” refers to a characteristic dimension ofan object. Thus, for example, a size of an object that is spherical canrefer to a diameter of the object. In the case of an object that isnon-spherical, a size of the non-spherical object can refer to adiameter of a corresponding spherical object, where the correspondingspherical object exhibits or has a particular set of derivable ormeasurable properties that are substantially the same as those of thenon-spherical object. Thus, for example, a size of a non-sphericalobject can refer to a diameter of a corresponding spherical object thatexhibits light scattering or other properties that are substantially thesame as those of the non-spherical object. Alternatively, or inconjunction, a size of a non-spherical object can refer to an average ofvarious orthogonal dimensions of the object. Thus, for example, a sizeof an object that is a spheroidal can refer to an average of a majoraxis and a minor axis of the object. When referring to a set of objectsas having a particular size, it is contemplated that the objects canhave a distribution of sizes around the particular size. Thus, as usedherein, a size of a set of objects can refer to a typical size of adistribution of sizes, such as an average size, a median size, or a peaksize.

As used herein, mallet or hammer refers to an orthopedic device made ofstainless steel or other dense material having a weight generally acarpenter's hammer and a stonemason's lump hammer.

As used herein, an impact force for impacting an acetabular component(e.g., an acetabular cup prosthesis) includes forces from striking animpact rod multiple times with the orthopedic device that are generallysimilar to the forces that may be used to drive a three inch nail into apiece of lumber using the carpenter's hammer by striking the nailapproximately a half-dozen times to completely seat the nail. Withoutlimiting the preceding definition, a representative value in someinstances includes a force of approximately 10 lbs./square inch.

As used herein, the term “real-time” sensing means sensing relevantparameters (e.g., force, acceleration, vibration, acoustic, and thelike) during processing.

The following description relates to improvements in a wide range ofprostheses installations into live bones of patients of surgeons. Thefollowing discussion focuses primarily on total hip replacement (THR) inwhich an acetabular cup prosthesis is installed into the pelvis of thepatient. This cup is complementary to a ball and stem (i.e., a femoralprosthesis) installed into an end of a femur engaging the acetabulumundergoing repair.

Embodiments of the present invention may include one of more solutionsto the above problems. The incorporated U.S. Pat. No. 9,168,154 includesa description of several embodiments, sometimes referred to herein as aBMD3 device, some of which illustrate a principle for breaking downlarge forces associated with the discrete blows of a mallet into aseries of small taps, which in turn perform similarly in a stepwisefashion while being more efficient and safer. The BMD3 device producesthe same displacement of the implant without the need for the largeforces from the repeated impacts from the mallet. The BMD3 device mayallow modulation of force required for cup insertion based on bonedensity, cup geometry, and surface roughness. Further, a use of the BMD3device may result in the acetabulum experiencing less stress anddeformation and the implant may experience a significantly smoothersinking pattern into the acetabulum during installation. Someembodiments of the BMD3 device may provide a superior approach to theseproblems, however, described herein are two problems that can beapproached separately and with more basic methods as an alternative to,or in addition to, a BMD3 device. An issue of undesirable torques andmoment arms is primarily related to the primitive method currently usedby surgeons, which involves manually banging the mallet on the impactionplate. The amount of force utilized in this process is alsonon-standardized and somewhat out of control.

With respect to the impaction plate and undesirable torques, anembodiment of the present invention may include a simple mechanicalsolution as an alternative to some BMD3 devices, which can be utilizedby the surgeon's hand or by a robotic machine. A direction of the impactmay be directed or focused by any number of standard techniques (e.g.,A-frame, C-arm or navigation system). Elsewhere described herein is arefinement of this process by considering directionality in the reamingprocess, in contrast to only considering it just prior to impaction.First, we propose to eliminate the undesirable torques by delivering theimpacts by a sledgehammer device (or a hollow cylindrical mass) thattravels over a stainless rod.

As noted in the background, the surgeon prepares the surface of thehipbone which includes attachment of the acetabular prosthesis to thepelvis. Conventionally, this attachment includes a manual implantationin which a mallet is used to strike a tamp that contacts some part ofthe acetabular prosthesis. Repeatedly striking the tamp drives theacetabular prosthesis into the acetabulum. Irrespective of whethercurrent tools of computer navigation, fluoroscopy, robotics (and otherintra-operative measuring tools) have been used, it is extremelyunlikely that the acetabular prosthesis will be in the correctorientation once it has been seated to the proper depth by the series ofhammer strikes. After manual implantation in this way, the surgeon thenmay apply a series of adjusting strikes around a perimeter of theacetabular prosthesis to attempt to adjust to the desired orientation.Currently such post-impaction result is accepted as many surgeonsbelieve that post-impaction adjustment creates an unpredictable andunreliable change which does not therefore warrant any attempts forpost-impaction adjustment.

In most cases, any and all surgeons including an inexperienced surgeonmay not be able to achieve the desired orientation of the acetabularprosthesis in the pelvis by conventional solutions due tounpredictability of the orientation changes responsive to theseadjusting strikes. As noted above, it is most common for any surgeon toavoid post-impaction adjustment as most surgeons understand that they donot have a reliable system or method for improving any particularorientation and could easily introduce more/greater error. The computernavigation systems, fluoroscopy, and other measuring tools are able toprovide the surgeon with information about the current orientation ofthe prosthesis during an operation and after the prosthesis has beeninstalled and its deviation from the desired orientation, but thenavigation systems (and others) do not protect against torsional forcescreated by the implanting/positioning strikes. The prosthesis will findits own position in the acetabulum based on the axial and torsionalforces created by the blows of the mallet. Even those navigation systemsused with robotic systems (e.g., MAKE) that attempt to secure an implantin the desired orientation prior to impaction are not guaranteed toresult in the installation of the implant at the desired orientationbecause the actual implanting forces are applied by a surgeon swinging amallet to manually strike the tamp.

A Behzadi Medical Device (BMD) is herein described and enabled thateliminates this crude method (i.e., mallet, tamp, and surgeon-appliedmechanical implanting force) of the prosthesis (e.g., the acetabularcup). A surgeon using the BMD is able to insert the prosthesis exactlywhere desired with proper force, finesse, and accuracy. Depending uponimplementation details, the installation includes insertion of theprosthesis into patient bone, within a desired threshold of metrics forinsertion depth and location) and may also include, when appropriateand/or desired, positioning at a desired orientation with the desiredthreshold further including metrics for insertion orientation). The useof the BMD reduces risks of fracturing and/or shattering the bonereceiving the prosthesis and allows for rapid, efficient, and accurate(atraumatic) installation of the prosthesis. The BMD provides a viableinterface for computer navigation assistance (also useable with allintraoperative measuring tools including fluoroscopy) during theinstallation as a lighter more responsive touch may be used.

The BMD encompasses many different embodiments for installation and/orpositioning of a prosthesis and may be adapted for a wide range ofprostheses in addition to installation and/or positioning of anacetabular prosthesis during THR.

FIG. 1-FIG. 6 illustrate a set of graphs of Force (y-axis) versusdistance (x-axis). FIG. 1 illustrates a set of “cup prints” for a numberof interactions between a cup and a cavity. Each combination of animplant (e.g., an acetabular cup) and its implant site (e.g., a reamedcavity in an acetabulum) has a resistive force (FR) that may be thoughtof as a particular cup print unique for that combination. FIG. 1includes four such cup prints. Factors influencing the cup print includebone density (hard/soft), cup geometry (elliptical/spherical), cupsurface preparation (e.g., roughness), and reaming preparation. Othersensors or sets of sensors may produce a more complex characteristicsensor print for processing of a prosthesis or portion of a prosthesis.

FIG. 2 illustrates a particular one representative cup print thatrelates to one cup/cavity interaction. FIG. 3 illustrates a controlledmodulated installation force envelope superimposed over the cup print ofFIG. 2. Typically, the amplitude of the modulation increases as theimplant is seated, with too great of force increasing a risk of fractureand tool little force increasing a risk of poor “seatedness”—a propertyof the implant relating to how well seated it is within its installationsite.

FIG. 4 illustrates an example installation force envelope that isrepresentative of use of a mallet in its production. In this example, asurgeon “feels” and “listens” for the magic zone—adequate insertion andgood pull-out force (seatedness) while being concerned with every strikethat the installation site may fracture. The non-controlledmallet-applied installation force is shown superimposed over the cupprint of FIG. 2.

FIG. 5 illustrates an example installation force envelope that isrepresentative of use of a BMD3 in its production. In this example, asurgeon dials into the magic zone by gradually changing the BMD3force-applied profile. A BMD3 controlled modulated installation forceenvelope is shown superimposed over the cup print of FIG. 2. The surgeonis able to use a BMD3-type tool to walk the envelope (the contour of theinstallation force envelope) up and into the magic zone with greatlyimproved confidence of achieving the desired seatedness without greatlyincreasing a risk of fracture. Frictional forces may be decreased(effectively and realistically) at certain frequencies that may improveas the frequency increases (e.g., one to hundreds of Hertz or more,one-two kilohertz or more, and beyond to ultrasonic frequencies abovetwo kilohertz). The reduced frictional forces may also enable easieralignment of the cup during and/or after insertion/placement.

FIG. 6 illustrates an example installation force envelope that isrepresentative of use of a BMD4 in its production. In this example, asurgeon dials into the magic zone by dialing the BMD4 force-appliedprofile. A BMD4 controlled modulated installation force envelope isshown superimposed over the cup print of FIG. 2. The surgeon is able touse a BMD4-type tool to dial into the magic zone (the contour of theinstallation force envelope) with greatly improved confidence ofachieving the desired seatedness without greatly increasing a risk offracture and while maintaining a desired alignment/positioning, forexample, within the Lewinski range.

A hybrid BMD3/BMD4 embodiment may provide a hybrid controlled modulatedinstallation force envelope that offers advantages of both BMD3 andBMD4.

FIG. 7 illustrates a representative installation gun. The installationgun may be operable with operable using pneumatics, though otherimplementations may use other mechanisms including motors for creating adesired vibratory motion of prosthesis to be installed.

The installation gun may be used to control precisely one or both of (i)insertion, and (ii) abduction and anteversion angles of a prostheticcomponent. Installation gun 100 preferably allows both installation ofan acetabular cup into an acetabulum at a desired depth and orientationof the cup for both abduction and anteversion to desired values.

The installation gun may include a controller with a handle supportingan elongate tube that terminates in an adapter that engages a cup.Operation of a trigger may initiate a motion of the elongate tube. Thismotion is referred to herein as an installation force and/orinstallation motion that is much less than the impact force used in aconventional replacement process. An exterior housing allows theoperator to hold and position the prosthesis (e.g., the cup) whileelongate tube moves within. Some embodiments may include a handle orother grip in addition to or in lieu of the housing that allows theoperator to hold and operate installation gun without interfering withthe mechanism that provides a direct transfer of installation motion tothe prosthesis. The illustrated embodiment may include the prosthesisheld securely by adapter allowing a tilting and/or rotation of gun aboutany axis to be reflected in the position/orientation of the securedprosthesis.

The installation motion includes constant, cyclic, periodic, and/orrandom motion (amplitude and/or frequency) that allows the operator toinstall the cup into the desired position (depth and orientation)without application of an impact force. There may be continuous movementor oscillations in one or more of six degrees of freedom includingtranslation(s) and/or rotation(s) of adapter 146 about the X, Y, Z axes(e.g., oscillating translation(s) and/or oscillating/continuousrotation(s) which could be different for different axes such astranslating back and forth in the direction of the longitudinal axis ofthe central support while rotating continuously around the longitudinalaxis). This installation motion may include continuous or intermittentvery high frequency movements and oscillations of small amplitude thatallow the operator to easily install the prosthetic component in thedesired location, and preferably also to allow the operator to also setthe desired angles for abduction and anteversion.

In some implementations, the controller includes a stored programprocessing system that includes a processing unit that executesinstructions retrieved from memory. Those instructions could control theselection of the motion parameters autonomously to achieve desiredvalues for depth, abduction and anteversion entered into by the surgeonor by a computer aided medical computing system such as the computernavigation system. Alternatively, those instructions could be used tosupplement manual operation to aid or suggest selection of the motionparameters.

For more automated systems, consistent and unvarying motion parametersare not required, and it may be that a varying dynamic adjustment of themotion parameters better conform to an adjustment profile of the cupinstalled into the acetabulum and status of the installation. Anadjustment profile is a characterization of the relative ease by whichdepth, abduction and anteversion angles may be adjusted in positive andnegative directions. In some situations, these values may not be thesame and the installation gun could be enhanced to adjust for thesedifferences. For example, a unit of force applied to pure positiveanteversion may adjust anteversion in the positive direction by a firstunit of distance while under the same conditions that unit of forceapplied to pure negative anteversion may adjust anteversion in thenegative direction by a second unit of distance different from the firstunit. And these differences may vary as a function of the magnitude ofthe actual angle(s). For example, as the anteversion increases it may bethat the same unit of force results in a different responsive change inthe actual distance adjusted. The adjustment profile when used helps theoperator when selecting the actuators and the impact force(s) to beapplied. Using a feedback system of the current real-time depth andorientation enables the adjustment profile to dynamically select/modifythe motion parameters appropriately during different phases of theinstallation. One set of motion parameters may be used when primarilysetting the depth of the implant and then another set used when thedesired depth is achieved so that fine tuning of the abduction andanteversion angles is accomplished more efficiently, all without use ofimpact forces in setting the depth and/or angle adjustment(s).

This device better enables computer navigation as theinstallation/adjustment forces are reduced as compared to the impactingmethod. This makes the required forces more compatible with computernavigation systems used in medical procedures which do not have thecapabilities or control systems in place to actually provide impactingforces for seating the prosthetic component. And without that, thecomputer is at best relegated to a role of providing after-the-factassessments of the consequences of the surgeon's manual strikes of theorthopedic mallet. (Also provides information before and during theimpaction. It is a problem that the very act of impaction introducesvariability and error in positioning and alignment of the prosthesis.

FIG. 7 illustrates a representative installation system 700 including apulse transfer assembly 705 and an oscillation engine 710; FIG. 8illustrates a disassembly of second representative installation system700; FIG. 9 illustrates a first disassembly view of pulse transferassembly 705; and FIG. 10 illustrates a second disassembly view of pulsetransfer assembly 705 of installation system 700.

Installation system 700 is designed for installing a prosthesis that, inturn, is configured to be implanted into a portion of bone at a desiredimplantation depth. The prosthesis includes some type of attachmentsystem (e.g., one or more threaded inserts, mechanical coupler, link, orthe like) allowing the prosthesis to be securely and rigidly held by anobject such that a translation and/or a rotation of the object about anyaxis results in a direct corresponding translation and/or rotation ofthe secured prosthesis.

Oscillation engine 710 includes a controller coupled to a vibratorymachine that generates an original series of pulses having a generationpattern. This generation pattern defines a first duty cycle of theoriginal series of pulses including one or more of a first pulseamplitude, a first pulse direction, a first pulse duration, and a firstpulse time window. This is not to suggest that the amplitude, direction,duration, or pulse time window for each pulse of the original pulseseries are uniform with respect to each other. Pulse direction mayinclude motion having any of six degrees of freedom—translation alongone or more axes of any axis of three orthogonal axes and/or rotationabout one or more of these three axes. Oscillation engine 710 includesan electric motor powered by energy from a battery, though other motorsand energy sources may be used.

Pulse transfer assembly 705 includes a proximal end 715 coupled tooscillation engine 710 and a distal end 720, spaced from proximal end720, coupled to the prosthesis using a connector system 725. Pulsetransfer assembly 705 receives the original series of pulses fromoscillation engine 710 and produces, responsive to the original seriesof pulses, an installation series of pulses having an installationpattern. Similar to the generation pattern, the installation patterndefines a second duty cycle of the installation series of pulsesincluding a second pulse amplitude, a second pulse direction, a secondpulse duration, and a second pulse time window. Again, this is not tosuggest that the amplitude, direction, duration, or pulse time windowfor each pulse of the installation pulse series are uniform with respectto each other, nor does it imply that they are non-uniform. Pulsedirection may include motion having any of six degrees offreedom—translation along one or more of any axes of three orthogonalaxes and/or rotation about one or more of these three axes.

For some embodiments of pulse transfer assembly 705, the installationseries of pulses will be strongly linked to the original series andthere will be a close match, if not identical match, between the twoseries. Some embodiments may include a more complex pulse transferassembly 705 that produces an installation series that is moredifferent, or very different, from the original series.

Connector system 725 (e.g., one or more threaded studs complementary tothe threaded inserts of the prosthesis, or other complementarymechanical coupling system) is disposed at proximal end 720. Connectorsystem 725 is configured to secure and rigidly hold the prosthesis. Inthis way, the attached prosthesis becomes a secured prosthesis whenengaged with connector system 725.

Pulse transfer assembly 705 communicates the installation series ofpulses to the secured prosthesis and produces an applied series ofpulses that are responsive to the installation series of pulses. Similarto the generation pattern and the installation pattern, the appliedpattern defines a third duty cycle of the applied series of pulsesincluding a third pulse amplitude, a third pulse direction, a thirdpulse duration, and a third pulse time window. Again, this is not tosuggest that the amplitude, direction, duration, or pulse time windowfor each pulse of the applied pulse series are uniform with respect toeach other. Pulse direction may include motion having any of six degreesof freedom—translation along one or more of any axes of three orthogonalaxes and/or rotation about one or more of these three axes.

For some embodiments of pulse transfer assembly 705, the applied seriesof pulses will be strongly linked to the original series and/or theinstallation series and there will be a close, if not identical, matchbetween the series. Some embodiments may include a more complex pulsetransfer assembly 705 that produces an applied series that is moredifferent, or very different, from the original series and/or theinstallation series. In some embodiments, for example one or morecomponents may be integrated together (for example, integratingoscillation engine 710 with pulse transfer assembly 705) so that thefirst series and the second series, if they exist independently arenearly identical if not identical).

The applied series of pulses are designed to impart a vibratory motionto the secured prosthesis that enable an installation of the securedprosthesis into the portion of bone to within 95% of the desiredimplantation depth without a manual impact. That is, in operation, theoriginal pulses from oscillation engine 710 propagate through pulsetransfer assembly 705 (with implementation-depending varying levels offidelity) to produce the vibratory motion to the prosthesis secured toconnector system 725. In a first implementation, the vibratory motionallows implanting without manual impacts on the prosthesis and in asecond mode an orientation of the implanted secured prosthesis may beadjusted by rotations of installation system 700 while the vibratorymotion is active, also without manual impact. In some implementations,the pulse generation may produce different vibratory motions optimizedfor these different modes.

Installation system 700 includes an optional sensor 730 (e.g., a flexsensor or the like) to provide a measurement (e.g., quantitative and/orqualitative) of the installation pulse pattern communicated by pulsetransfer assembly 705. This measurement may be used as part of a manualor computerized feedback system to aid in installation of a prosthesis.For example, in some implementations, the desired applied pulse patternof the applied series of pulses (e.g., the vibrational motion of theprosthesis) may be a function of a particular installation pulsepattern, which can be measured and set through sensor 730. In additionto, or alternatively, other sensors may aid the surgeon or an automatedinstallation system operating installation system 700, such as a bonedensity sensor or other mechanism to characterize the bone receiving theprosthesis to establish a desired applied pulse pattern for optimalinstallation. In some implementations, sensor 730 measures forcemagnitude as part of the installation pulse pattern.

The disassembled views of FIG. 9 and FIG. 10 detail a particularimplementation of pulse transfer assembly 705, it being understood thatthere are many possible ways of creating and communicating an appliedpulse pattern responsive to a series of generation pulses from anoscillation engine. The illustrated structure of FIG. 9 and FIG. 10generate primarily longitudinal/axial pulses in response to primarilylongitudinal/axial generation pulses from oscillation engine 710.

Pulse transfer assembly 705 includes an outer housing 735 containing anupper transfer assembly 940, a lower transfer assembly 945 and a centralassembly 950. Central assembly 950 includes a double anvil 955 thatcouples upper transfer assembly 940 to lower transfer assembly 945.Outer housing 935 and central assembly 950 each include a port allowingsensor 930 to be inserted into central assembly 950 between an end ofdouble anvil 955 and one of the upper/lower transfer assemblies.

Upper transfer assembly 940 and lower transfer assembly 945 each includea support 960 coupled to outer housing 735 by a pair of connectors. Atransfer rod 965 is moveably disposed through an axial aperture in eachsupport 960, with each transfer rod 965 including a head at one endconfigured to strike an end of double anvil 955 and a coupling structureat a second end. A compression spring 970 is disposed on each transferrod 965 between support 960 and the head. The coupling structure ofupper transfer assembly 940 cooperates with oscillation engine 710 toreceive the generated pulse series. The coupling structure of lowertransfer assembly 945 includes connector system 725 for securing theprosthesis. Some embodiments may include an adapter, not shown, thatadapts connector system 725 to a particular prosthesis, differentadapters allowing use of pulse transfer assembly 705 with differentprosthesis.

Central assembly 950 includes a support 975 coupled to outer housing 735by a connector and receives double anvil 955 which moves freely withinsupport 975. The heads of the upper transfer assembly and the lowertransfer assembly are disposed within support 975 and arranged to strikecorresponding ends of double anvil 955 during pulse generation.

In operation, oscillation engine 710 generates pulses that aretransferred via pulse transfer assembly 705 to the prosthesis secured byconnector system 725. The pulse transfer assembly 705, via uppertransfer assembly 940, receives the generated pulses using transfer rod965. Transfer rod 965 of upper transfer assembly 940 moves withinsupport 960 of upper transfer assembly 940 to communicate pulses todouble anvil 955 moving within support 975. Double anvil 955, in turn,communicates pulses to transfer rod 965 of lower transfer assembly 945to produce vibratory motion of a prosthesis secured to connector system725. Transfer rods 965 move, in this illustrated embodiment, primarilylongitudinally/axially within outer housing 735 (a longitudinal axisdefined as extending between proximate end 715 and distal end 720. Inthis way, the surgeon may use outer housing 735 as a hand hold wheninstalling and/or positioning the vibrating prosthesis.

The use of discrete transfer portions (e.g., upper, central, and lowertransfer assemblies) for pulse transfer assembly 705 may allow a form ofloose coupling between oscillation engine 710 and a secured prosthesis.In this way pulses from oscillation engine 710 are converted into avibratory motion of the prosthesis as it is urged into the bone duringoperation. Some embodiments may provide a stronger coupling by directlysecuring one component to another, or substituting a single componentfor a pair of components.

The embodiment of FIG. 7 has demonstrated insertion of a prosthetic cupinto a bone substitute substrate with ease and a greatly reduced forceas compared to use of a mallet and tamp, especially as no impaction wasrequired. While the insertion was taking place and vibrational motionwas present at the prosthesis, the prosthesis could be positioned withrelative ease by torqueing on a handle/outer housing to an exact desiredalignment/position. The insertion force is variable and ranges between20 to 800 pounds of force. Importantly the potential for use ofsignificantly smaller forces in application of the prosthesis (in thiscase the acetabular prosthesis) in bone substrate with the presentinvention is demonstrated to be achievable.

Installation system 700 may include an oscillation engine producingpulses at approximately 60 Hz. System 700 operated at 60 Hz. In testing,approximately 4 seconds of operation resulted in a desired insertion andalignment of the prosthesis (meaning about 240 cycles of the oscillationengine). Conventional surgery using a mallet striking a tamp to impactthe cup into place is generally complete after 10 blows of themallet/hammer.

Experimental

System 700 was tested in a bone substitute substrate with a standardZimmer acetabular cup using standard technique of under reaming aprepared surface by 1 mm and inserting a cup that was one millimeterlarger. The substrate was chosen as the best option available to studythis concept, namely a dense foam material. It was recognized thatcertain properties of bone would not be represented here (e.g. less ofan ability of the bone substrate to stretch before failure).

FIG. 7 demonstrated easy insertion and positioning of the prosthetic cupwithin the chosen substrate. We were able to move the cup in thesubstrate with relative ease. There was no requirement for a mallet orhammer for application of a large impact. These experiments demonstratedthat the prosthetic cups could be inserted in bone substitute substrateswith significantly less force and more control than what could be donewith blows of a hammer or mallet. We surmise that the same phenomena canbe reproduced in human bone. We envision the prosthetic cup beinginserted with ease with very little force.

Additionally, we believe that simultaneously, while the cup is beinginserted, the position of the cup can be adjusted under directvisualization with any intra-operative measurement system (navigation,fluoroscopy, and the like.). This invention provides a system thatallows insertion of a prosthetic component with NON-traumatic force(insertion) as opposed to traumatic force (impaction).

Experimental Configuration—System 700

Oscillation engine 710 included a Craftsman GO Hammerhead nailed used todrive fairly large framing nails into wood in confined spaces byapplying a series of small impacts very rapidly in contrast toapplication of few large impacts.

The bone substitute was 15-pound density urethane foam to represent thepelvic acetabulum. It was shaped with a standard cutting tool commonlyused to clean up a patient's damaged acetabulum. A 54 mm cup and a 53 mmcutter were used in testing.

In one test, the cup was inserted using a mallet and tamp, withimpaction complete after 7 strikes. Re-orientation of the cup wasrequired by further strikes on a periphery of the cup after impaction toachieve a desired orientation. It was qualitatively determined that thefeel and insertion were consistent with impaction into bone.

An embodiment of system 700 was used in lieu of the mallet and tampmethod. Several insertions were performed, with the insertions found tobe much more gradual; allowing the cup to be guided into position (depthand orientation during insertion). Final corrective positioning iseasily achievable using lateral hand pressure to rotate the cup withinthe substrate while power was applied to the oscillation engine.

Further testing using the sensor included general static load detectiondone to determine the static (non-impact) load to push the cup into theprepared socket model. This provided a baseline for comparison to theimpact load testing. The prosthesis was provided above a prepared socketwith a screw mounted to the cup to transmit a force applied from a benchvise. The handle of the vice was turned to apply an even force tocompress the cup into the socket until the cup was fully seated. The cupbegan to move into the socket at about an insertion force of ˜200 poundsand gradually increased as diameter of cup inserted into socketincreased to a maximum of 375 pounds which remained constant until thecup was fully seated.

Installation system 700 was next used to install the cup into asimilarly prepared socket. Five tests were done, using different framerates and setup procedures, to determine how to get the most meaningfulresults. All tests used a 54 mm acetabular Cup. The oscillation engineran at an indicated 60 impacts/second. The first two tests were done at2,000 frames/second, which wasn't fast enough to capture all the impactevents but helped with designing the proper setup. Test 3 used theoscillation engine in an already used socket, 4,000 frames per second.Test 4 used the oscillation engine in an unused foam socket at 53 mm,4,000 frames per second.

Test 3: In already compacted socket, the cup was pulsed using theoscillation engine and the pulse transfer assembly. Recorded strikesbetween 500 and 800 lbs., with an average recorded pulse duration 0.8Ms.

Test 4: Into an unused 53 mm socket, the cup was pulsed using theoscillation engine and the pulse transfer assembly. Recorded impactsbetween 250 and 800 lbs., and an average recorded pulse duration 0.8 Ms.Insertion completed in 3.37 seconds, 202 impact hits.

Test 5: Into an unused 53 mm socket, the cup was inserted with standardhammer (for reference). Recorded impacts between 500 and 800 lbs., andan average recorded pulse duration 22.0 Ms. Insertion completed in 4seconds using 10 impact hits for a total pressure time of 220 Ms. Thistest was performed rapidly to complete it in 5 seconds for goodcomparability with tests 3 and 4 used 240 hits in 4 seconds, with asingle hit duration of 0.8 MS, for a total pressure time of 192 Ms.

Additionally, basic studies can further be conducted to correlate adensity and a porosity of bone at various ages (e.g., through a cadaverstudy) with an appropriate force range and vibratory motion patternrequired to insert a cup using the present invention. For example, asurgeon will be able to insert sensing equipment in patient bone, or useother evaluative procedures, (preoperative planning or while performingthe procedure for example) to assess porosity and density of bone. Onceknown, the density or other bone characteristic is used to set anappropriate vibratory pattern including a force range on an installationsystem, and thus use a minimal required force to insert and/or positionthe prosthesis.

BMD is a “must have” device for all medical device companies andsurgeons. Without BMD the Implantation problem is not addressed,regardless of the recent advances in technologies in hip replacementsurgery (i.e.; Navigation, Fluoroscopy, MAKE/robotics,accelerometers/gyro meters, etc.). Acetabular component (cup)positioning remains the biggest problem in hip replacement surgery.Implantation is the final step where error is introduced into the systemand heretofore no attention has been brought to this problem. Currenttechnologies have brought significant awareness to the position of theimplants within the pelvis during surgery, prior to impaction. However,these techniques do not assist in the final step of implantation.

BMD allows all real-time information technologies to utilize (a tool) toprecisely and accurately implant the acetabular component (cup) withinthe pelvic acetabulum. BMD device coupled with use of navigationtechnology and fluoroscopy and (other novel measuring devices) is theonly device that will allow surgeons from all walks of life, (lowvolume/high volume) to perform a perfect hip replacement with respect toacetabular component (cup) placement. With the use of BMD, surgeons canfeel confident that they are doing a good job with acetabular componentpositioning, achieving the “perfect cup” every time. Hence the BMDconcept eliminates the most common cause of complications in hipreplacement surgery which has forever plagued the surgeon, the patientsand the society in general.

It is known to use ultrasound devices in connection with some aspects ofTHR, primarily for implant removal (as some components may be installedusing a cement that may be softened using ultrasound energy). There maybe some suggestion that some ultrasonic devices that employ “ultrasound”energy could be used to insert a prosthesis for final fit, but it is inthe context of a femoral component and it is believed that these devicesare not presently actually used in the process). Some embodiments ofBMD, in contrast, can simply be a vibratory device (non-ultrasonic,others ultrasonic, and some hybrid impactful and vibratory), and is moreprofound than simply an implantation device as it is most preferably apositioning device for the acetabular component in THR. Further, thereis a discussion that ultrasound devices may be used to prepare bones forimplanting a prosthesis. BMD may address preparation of the bone in someaspects of the present invention.

Some embodiments BMD include devices that concern themselves with properinstallation and positioning of the prosthesis (e.g., an acetabularcomponent) at the time of implanting of the prosthesis. Veryspecifically, it uses some form of vibratory energy coupled with avariety of “real-time measurement systems” to POSITION the cup in aperfect alignment with minimal use of force. A prosthesis, such as forexample, an acetabular cup, resists insertion. Once inserted, the cupresists changes to the inserted orientation. The BMDs of the presentinvention produce an insertion vibratory motion of a secured prosthesisthat reduces the forces resisting insertion. In some implementations,the BMD may produce a positioning vibratory motion that reduces theforces resisting changes to the orientation. There are someimplementations that produce both types of motion, either as a singlevibratory profile or alternative profiles. In the present context forpurposes of the present invention, the vibratory motion is characterizedas “floating” the prosthesis as the prosthesis can become much simplerto insert and/or re-orient while the desired vibratory motion isavailable to the prosthesis. Some embodiments are described as producingvibrating prosthesis with a predetermined vibration pattern. In someimplementations, the predetermined vibration pattern is predictable andlargely completely defined in advance. In other implementations, thepredetermined vibration pattern includes randomized vibratory motion inone or more motion freedoms of the available degrees of freedom (up tosix degrees of freedom). That is, whichever translation or rotationalfreedom of motion is defined for the vibrating prosthesis, any of themmay have an intentional randomness component, varying from large tosmall. In some cases, the randomness component in any particular motionmay be large and, in some cases, predominate the motion. In other cases,the randomness component may be relatively small as to be barelydetectable.

A tool, among others, that may support the force measurement includes anaxially-impactful Behzadi Medical Device (BMD4). The BMD4 may include amoveable hammer sliding axially and freely along a rod. The rod mayinclude a proximal stop and a distal stop. These stops that may beintegrated into rod allow transference of force to rod when the hammerstrikes the distal stop. At a distal end of the rod, the device includesan attachment system for a prosthesis. For example, when the prosthesisincludes an acetabular cup having a threaded cavity, the attachmentsystem may include a complementary threaded structure that screws intothe threaded cavity. The illustrated design of the device allows only aperfect axial force to be imparted. The surgeon cannot deliver a blow tothe edge of an impaction plate. Therefore, the design of this instrumentis in and of itself protective, eliminating a problem of “surgeon'smallet hitting on the edge of the impaction plate” or other mis-alignedforce transference, and creating undesirable torques, and henceunintentional mal-alignment of the prosthesis from an intendedposition/orientation. This embodiment may be modified to include avibratory engine as described herein.

The embodiment may include a pressure sensor to provide feedback duringinstallation. With respect to management of the vibration/force requiredfor some of these tasks, it is noted that with current techniques (theuse of the mallet) the surgeon has no indication of how much force isbeing imparted onto the implant and/or the implant site (e.g., thepelvis). Laboratory tests may be done to estimate what range of forceshould be utilized in certain age groups (as a rough guide) and thenfashioning a device 1100, for example a modified sledgehammer or acockup gun to produce just the right amount of force and/or producing apredetermined force of a known magnitude. Typically, the surgeon may useup to 2000N to 3000N of force to impact a cup into the acetabularcavity. Also, since some embodiments cannot deliver the force in anincremental fashion as described in association with the BMD3 device,the device may include a stopgap mechanism. Some embodiments of the BMD3device have already described the application of a sensor in the body ofthe impaction rod. The device may include a sensing system/assemblyembedded in the device, for example proximate the rod near the distalend, and used to provide valuable feedback information to the surgeon.The pressure sensor can let the surgeon know when the pressures seem tohave maximized, whether used for the insertion of an acetabular cup, orany other implant including knee and shoulder implants and rods used tofix tibia and femur fractures. When the pressure sensor is not showingan advance or increase in pressure readings and has plateaued, thesurgeon may determine it is time to stop operation/impacting. Anindicator, for example an alarm can go off or a red signal can show whenmaximal peak forces are repeatedly achieved. As noted above, theincorporated patents describe a presence of a pressure sensor in aninstallation device, the presence of which was designed as part of asystem to characterize an installation pulse pattern communicated by apulse transfer assembly. The disclosure here relates to a pressuresensor provided not to characterize the installation vibration/pulsepattern but to provide an in-situ feedback mechanism to the surgeon asto a status of the installation, such as to reduce a risk of fracturingthe installation site. Some embodiments may also employ this pressuresensor for multiple purposes including characterization of an appliedpulse pattern such as, for example, when the device includes automatedcontrol of an impacting engine coupled to the hammer. Other embodimentsof this invention may dispose the sensor or sensor reading system withina handle or housing of the device rather than in the central rod orshaft.

Previous work has sought to address the two problems noted aboveculminating in a series of devices identified as BMD2, BMD3, and BMD4,collectively herein representative of examples of an insertion agency.Each of these systems attempts to address the two problems noted abovewith different and novel methods.

The BMD2 concept proposed a system of correcting a cup (acetabularimplant) that had already been implanted in a mis-aligned position. Itbasically involves a gun like tool with a central shaft and peripheralactuators, which attaches to an already implanted cup with the use of anadaptor. Using computer navigation, through a series of calculations,pure points (specifically defined) and secondary points on the edge ofthe cup are determined. This process confers positional information tothe edge of the cup. The BMD2 tool has actuators that correspond tothese points on the cup, and through a computer program, the appropriateactuators impact on specific points on the edge of the cup to adjust theposition of the implanted cup. The surgeon dials in the desiredalignment and the BMD2 tool fires the appropriate actuators to realignthe cup to the perfect position.

In BMD3, we considered that vibratory forces may be applied in a mannerto disarm frictional forces in insertion of the acetabular cup into thepelvis. We asked the following questions: Is it possible to insert andposition the cup into the pelvis without high energy impacts? Is itpossible to insert the cup using vibratory energy? Is insertion andsimultaneous alignment and positioning of the cup into the pelvispossible? BMD3 prototypes were designed and the concept of vibratoryinsertion was proven. It was possible to insert the cup with vibratoryenergy. The BMD3 principle involved the breaking down of the largemomentum associated with the discrete blows of the mallet into a seriesof small taps, which in turn did much of the same work incrementally,and in a stepwise fashion. We considered that this method allowedmodulation of force required for cup insertion. In determining theamount of force to be applied, we studied the resistive forces involvedin a cup/cavity interaction. We determined that there are severalfactors that produce the resistive force to cup insertion. These includebone density (hard or soft), cup geometry (spherical or elliptical), andsurface roughness of the cup. With the use of BMD3 vibratory insertion,we demonstrated through FEM studies, that the acetabulum experiencesless stress and deformation and the cup experiences a significantlysmoother sinking pattern. We discovered the added benefit of ease ofmovement and the ability to align the cup with the BMD3 vibratory tool.During high frequency vibration the frictional forces are disarmed inboth effective and realistic ways, (see previous papers-periodic staticfriction regime, kinetic friction regime). We have also theorized thatcertain “mode shapes” (preferred directions of deformation) can beelicited with high frequency vibration to allow easy insertion andalignment of the cup. The pelvis has a resonant frequency and is aviscoelastic structure. Theoretically, vibrations can exploit theelastic nature of bone and its dynamic response. This aspect ofvibratory insertion can be used to our advantage in cup insertion anddeserves further study. Empirically, the high frequency aspect of BMD3allows easy and effortless movement and insertion of the cup into thepelvis. This aspect BMD3 is clinically significant allowing the surgeonto align the cup in perfect position while the vibrations are occurring.

The BMD4 idea was described to address the two initial problems(uncontrolled force and undesirable torques) in a simpler manner. Theundesirable torque and mis-alignment problem from mallet blows wereneutralized with the concept of the “slide-hammer” which only allowsaxial exertion of force. With respect to the amount of force, BMD4allowed the breaking down of the large impaction forces (associated withthe use of the mallet) into quantifiable and smaller packets of force.The delivery of this force occurs through a simple slide-hammer, cockupgun, robotic tool, electric or pneumatic gun (all of which deliver asliding mass over a central coaxial shaft attached to the impaction rodand cup. In the BMD4 paper we described two “stop gap” mechanisms toprotect the pelvis from over exertion of force. We described a pressuresensor in the shaft of the BMD4 tool that monitors the force pressure inthe (tool/cup system). This force sensor would determine when thepressure had plateaued indicating the appropriate time to stop themanual impacts. We also described a pitch/sound sensor in the room,attached to the gun or attached to the pelvis that would assess when thepitch is not advancing, alerting the surgeon to stop applying force.These four aspects of BMD4 (coaxially of the gun, quantification andcontrol of the force, a force sensor, a sound sensor) are separated andindependent functions which can could be used alone or in conjunctionwith each other.

We also recommended that BMD4's (coaxiality and force control function)and BMD3's (vibratory insertion) be utilized for application of femoraland humeral heads to trunnions, to solve the trunnionosis problem.

Materials and Methods: During our development, we evaluated differentaspects of the BMD3 and BMD4 prototypes. With BMD3 concept we sought tostudy several aspects of vibratory insertion:

1. The ultimate effect of frequency on cup insertion.

2. The range of impact forces achievable with vibratory insertion.

3. The effect of frequency and vibratory impaction forces on cupinsertion and (extraction forces measured to assess the quality ofinsertion).

With Respect to BMD4 we studied the various aspects of “controlledimpaction” utilizing Drop Tests (dynamic testing) and Instron Machine(static testing) to determine the behavior of cup/cavity interaction.

Results:

BMD3

Preliminary results suggest that vibratory insertion of the cup into abone substitute is possible. It is clear that vibratory insertion athigher frequencies allow easy insertion and alignment of the cup inbone.

It is unclear as to how much higher frequencies contribute to the depthand quality of insertion, as measured by the extraction force,particularly as the cup is inserted deeper into the substrate.

We determined that with vibrational insertion, the magnitude ofimpaction force is limited and dependent on other mechanical factorssuch as frequency of vibration and the dwell time. So far 400 lbs. offorce have been achieved with the BMD/BE prototype, 250 lbs. of forcehave been achieved with the auto hammer prototype, and 150 lbs. of forcehave been achieved by the pneumatic prototype. Further work is underwayto determine the upper limit of achievable forces with the Vibrationaltools.

During our study of Vibrational insertion, we also discovered thatvibrational insertion can be unidirectional or bidirectional. Forinsertion of the cup into a substrate it was felt that unidirectionalvibratory insertion (in a positive direction) is ideal. We discoveredthat unidirectional vibratory withdrawal and bidirectional vibrationhave other applications such as in revision surgery, preparation ofbone, and for insertion of bidirectional prosthetic cups. Thedirectionality of the BMD3 vibratory prototype and its applications willbe further discussed in additional applications.

BMD4

With respect to controlled impacts we sought to understand thecup/cavity interaction in a more comprehensive way. We wanted todiscover the nature of the resistive forces involved in a cup/cavityinteraction. We felt it was necessary for us to know this information inorder to be able to produce the appropriate amount of force for bothBMD3 “vibratory insertion” and BMD4 “controlled impaction”. We proposedand conducted dynamic Drop tests and static Instron tests to evaluatethe relationship between the cup and the cavity. Instron testing isunderway and soon to be completed. The drop tests were conducted using aZimmer continuum 62 mm cup and 20 lbs. urethane foam. Multiple droptests were conducted at various impaction forces to evaluate therelationship between applied force (TMIF) and displacement of the cup,and the quality of insertion (Extraction Force). We discovered that forinsertion of a cup into a cavity the total resistive force can begenerally represented by an exponential curve. We have termed thisresistive force the FR, which is determined by measuring therelationship of applied force (TMIF) and cup insertion for anyparticular (cup/cavity) system. FR is a function of several factorsincluding the spring like quality of bone which applies a compressiveresistive force (Hooke's law F=kx) to the cup, the surface roughness'sof the cup, an amount of under reaming, and the geometry of the cup(elliptical v spherical).

Definitions: FR=Force Resistance (total resistive force to cup insertionover full insertion of the cup into bone substitute); TMIF=TheoreticalMaximum Impact Force (external force applied to the system) toaccomplish cup insertion; and mIF=measured Impact Force (force measuredwithin the system) (as measured on the BMD3 and BMD4) tools.

BMD/BE vibratory prototype Auto hammer vibratory prototype Pneumaticvibratory prototype

Evaluation of the drop test data reveals a nonlinear (exponential) curvethat represents FR. We contemplated that the cup/cavity system we used(62 m Continuum cup and 20 lb. urethane foam) has a specific profile or“cup print”, and that this profile was important to know in advance sothat application of force can be done intelligently.

We observed the general shape of FR to be non-linear with three distinctsegments to the curve, which we have termed A, B, and C. In section Athe resistive force is low (from 100 to 350 lbs.) with a smaller slope.In section A, if an applied force (TMIF) greater than this FR isapplied, it can produce up to 55% cup insertion and 30% extractionforce. A TMIF that is tuned to cross FR at the A range is at risk forpoor seating and pull out. In section B the resistive forces range from500 lbs to 900 lbs. The slope rises rapidly and is significantly largerthan in section A (as expected in an exponential curve). In section B,if a TMIF greater than this FR is applied, it can produce between 74% to90% cup insertion and between 51% to 88% extraction force. We name thissection the “B cloud”, to signify that the applied force (TMIF) shouldgenerally be tuned to this level to obtain appropriate insertion withless risk for fracture and or pull out, regardless of whether the TMIFis applied by a BMD3 or BMD4 tool. In section C the curve asymptotes,with small incremental increase in cup insertion and large increases inextraction force. The clinical value of the higher extraction force isuncertain with increased risk of fracture. A TMIF that is tuned to crossthe FR at the C range is high risk for fracture and injury to thepelvis.

FIG. 12 relates to a Behzadi Medical Device (BMDX) which may combinevibratory and axial impactful forces from BMD3 and BMD4 among otheroptions; and FIG. 12 illustrates a Force Resistance (FR) curve forvarious experimental configurations, for example, force as a function ofdistance or displacement.

DISCUSSION

The FR curve represents a very important piece of information. To thesurgeon the FR curve should have the same significance that atopographical map has to a mountaineer. Knowing the resistive forcesinvolved in any particular cup/cavity interaction is desirable in orderto know how much force is necessary for insertion of the cup. We believethat in vitro, all cup/cavity interactions have to be studied andqualified. For example, it is important to know if the same 62 mmContinuum cup we used in this experiment is going to be used in a40-year-old or 70-year-old person. The variables that will determine FRinclude bone density which determines the spring like quality of bonethat provides compression to the cup, the geometry of the cup, an amountof under reaming, and the surface roughness of the cup. Once the FR fora particular cup and bone density is known, the surgeon is now armedwith information he/she can use to reliably insert the cup. This wouldseem to be a much better way to approach cup insertion than bangingclueless on an impaction rod with a 4 lbs mallet. Approaching FR with aneye for the B range will assure that the cup is not going to be poorlyseated with risk of pullout or too deeply seated with a risk offracture.

We have contemplated approaching FR with both vibratory (BMD3) insertionand controlled (BMD4 impaction) among other devices. Each of thesesystems has advantages and disadvantages that continue to be studied andfurther developed.

For example, we believe that vibratory insertion with the current BMD3prototypes have the clear advantage of allowing the surgeon ease ofmovement and insertion. The surgeon appears to be able to move the cupwithin the cavity by simple hand pressure to the desired alignment. Thisprovides the appearance of a frictionless state. However, to date wehave not quite been able to achieve higher forces with the BMD3 tools.So far, we have been able to achieve up to 150 lb. (pneumatic), 250(auto hammer), and 400 lb. (BMD/BE) in our vibratory prototypes. Thislevel of applied force provides submaximal level of insertion and pullout force. We believe that ultimately, higher forces can be achievedwith the vibratory BMD3 tools (500 to 900 lbs) which will provide fordeep and secure seating.

With regards to this concern, we have contemplated a novel approach toaddress the current technological deficits. We propose a combination ofBMD3 vibratory insertion with controlled BMD4 impaction. The BMD3vibratory tool (currently at 100 lbs. to 400 lbs) is used to initiatethe first phase of insertion allowing the surgeon to easily align andpartially insert the prosthesis with hand pressure, while monitoring thealignment with the method of choice (A-frame, navigation, C-arm, IMU).The BMD4 controlled impaction is then utilized to apply quantifiablepackets of force (100 lbs. to 900 lbs) to the cup to finish the seatingof the prosthesis in the B range of the FR curve. This can be doneeither as a single step fashion or “walking up the FR curve” fashion.

Alternatively, BMD4 controlled impaction can be utilized to insert thecup without the advantage of BMD3 tool. The BMD4 technique provides theability to quantify and control the amount of applied force (TMIF) andprovides coaxiality to avoid undesirable torques during the impaction.It is particularly appealing for robotic insertion where the position ofthe impaction rod is rigidly secured by the robot.

We have contemplated that the BMD4 controlled impaction can be utilizedin two separate techniques.

The first technique involves setting the impaction force within themiddle of the B Cloud where 74% to 90% insertion and 51% to 88%extraction forces could be expected, and then impacting the cup. TheBMD4 tool acts through the slide hammer mechanism to produce a specificamount of force (for example 600 lbs) and deliver it axially. This canbe considered a single step mechanism for use of BMD4 technique.

The second method involves “walking the forces” up the FR curve. In thissystem the applied force (TMIF) is provided in “packets of energy”. Forexample, the BMD4 gun may create 100 lbs packets of force. It has aninternal pressure sensing mechanism that allows the tool to know ifinsertion is occurring or not. A force sensor and a correspondingalgorithm within the BMD4 tool is described herein. The force sensormonitors the measured impact force (mIF) and the corresponding change inmIF within the system. As we have described before, when impacts areapplied to an “inelastic” system, energy is lost at the interface asinsertion occurs and heat is produced. This loss of energy is measuredand calculated in the (change) or slope of mIF. Consecutive mIF s haveto be measured and compared to previous mIFs to determine if insertionis occurring. As long as insertion is occurring impactions willcontinue. When the change in mIF approaches zero, insertion is notoccurring, there is no dissipation of energy within the system the slopeor (change) in mIF has approached zero. At this point the cup and cavitymove together as a rigid system (elastic), and all the kinetic energy ofTMIF is experienced by the cup/cavity system and mIF is measured to bethe same as TMIF. When insertion is not occurring mIF has approachedTMIF and change in mIF has approached zero.

At this point the next step is taken and TMIF is increased, for exampleby a packet of 100 lbs. The subsequent mIF measurements are taken and ifthe slope (change) in mIF is high, insertion is occurring with the newTMIF, therefore impacts should continue until the change in mIFapproaches zero again.

Conversely, if an increase in TMIF results in an increase in mIF but notthe change (slope) in mIF, we know the cup is no longer inserting andhas reached its maximum insertion point. We should point out that whenthe cup stops inserting, this also the point where FR exceeds TMIF. Inthis manner, we have contemplated an algorithm that allows formonitoring of the forces experienced in the system. Based on thisalgorithm, a system is created in which the surgeon can walk the TMIF upthe FR curve while being given real-time feedback information as to whento stop impaction.

The general idea is that at some point in time the cup will no longerinsert (even though not fully seated). This algorithm determines when nofurther insertion is occurring. The surgeon will be content to stopimpaction in the B cloud range of the FR curve.

We have also discovered that mIF is related to TMIF+FR. The value ofTMIF is known. The value of mIF is measured. The FR can be calculatedlive during insertion by the BMD3 and BMD4 tools and shown to thesurgeon as a % or (probability of fracture). This calculation andalgorithm could be very significant.

A few words on Alignment:

We have so far proposed that the BMD3 vibratory tool be used to insertthe cup under monitoring by current alignment techniques (navigation,

Fluoroscopy, A-frame). We have now devised a novel system, which webelieve will be the most efficacious method of monitoring and assuringalignment. This system relies of Radlink (X-rays) and PSI (patientspecific models) to set and calibrate the OR space as the first step.

As a second step, it utilizes a novel technique with use of IMUtechnology to monitor the movement of the reamers, tools (BMDs) andimpaction rods. This is discussed in a separate paper. Needs to bewritten up.

Summary and Recommendations for BMD/BE project.

1. We propose a novel system of inserting and aligning the acetabularcup in the human pelvic bone. This technique involves combining aspectsof the BMD3 and BMD4 prototypes, initially utilizing BMD3 vibratoryinsertion to partially insert and perfectly align the acetabular cupinto the pelvis. Subsequently switching to the BMD4 controlled impactiontechnique to apply specific quantifiable forces for full seating andinsertion. In this manner we are combining the proven advantages of thevibratory insertion prototype with the advantages of the controlledimpaction prototype.

2. We have described a force sensing system within the BMD tool withcapacity to measure the force experienced by the system (mIF) andcalculate the change in mIF with respect to time or number of impacts.This system provides a feedback mechanism for the BMD tools as to whenimpaction should stop.

3. We have described the FR curve which is a profile (cup print) of anycup/cavity interaction. And have recommended that this “cup print” formost cup/cavity interactions be determined in vitro to arm the surgeonwith information necessary for cup insertion. We feel that everycup/cavity interaction deserves study to determine its FR profile. Oncethe FR is known, BMD3 and BMD4 tools can be used to intelligently andconfidently apply force for insertion of the acetabular prosthesis.

4. We have described two methods for use of BMD4 controlled cupimpaction

a. Setting the TMIF to the middle of the B cloud (somewhere between 500to 900 range for our FR) and producing a single stage impaction.

b. Producing sequential packets of increasing TMIF in order to walk TMIFup the FR curve. (Increasing packets of 100 lbs or 200 lbs)

5. We have also discovered that mIF is related to TMIF+FR. The value ofTMIF is known. The value of mIF is measured. The FR can be calculatedlive during insertion by the BMD3 and BMD4 tools and shown to thesurgeon as a % or (probability of fracture). This calculation andalgorithm could be very significant in help the surgeon to insert thecup deeply without fracture.

Concept 5W and 1H:

1. Who: The surgeon; 2. What: Cup insertion; 3. When: When to increasethe force and when to stop; 4. Where: PSI and Radlink to set and IMU tomonitor alignment and position; 5. Why: Consistency for the surgeon andthe patient; and 6. How: FR for every cup/cavity interaction, BMD3 andBMD4 tools.

FIG. 13-FIG. 14 illustrate a general force measurement system 1300 forunderstanding an installation of a prosthesis P into an installationsite S (e.g., an acetabular cup into an acetabulum during total hipreplacement procedures); FIG. 13 illustrates an initial engagement ofprosthesis P to a cavity at installation site S when prosthesis P issecured to a force sensing tool 1305; FIG. 14 illustrates a partialinstallation of prosthesis P 13 into the cavity by operation of forcesensing tool 1305.

Tool 1305 includes an elongate member 1310, such as a shaft, rod, or thelike. There may be many different embodiments but tool 1305 may includea mechanism for direct or indirect measurement of impact forces (mIF)such as by inclusion of an in-line sensor 1315. Further, tool 1305allows for application of an external force applied to tool 1305. Insome embodiments, another sensor 1320 may be used to measure thisapplied force as a theoretical maximum impact force (TMIF). In somecases, the TMIF is applied from outside and in other systems, theapplication is from tool 1305 itself. In some cases, there system 1300has a priori knowledge of the force applied, or it can estimate itwithout use of sensor 1320. Depending upon an implementation, varioususer interface elements and controls may be included, includingindicators for various measured, calculated, and/or determined statusinformation.

During operation, as mIF begins to approach TMIF, then system 1300understands that prosthesis P is not moving much, if any, in response tothe TMIF (when it is kept relatively constant). An advantage to themechanical tools is their ability to repeatably apply aknown/predetermined force allowing for understanding of where theprocess is on an applicable FR curve for prosthesis P at installationsite S. For example, in FIG. 14, the mIF, for a constant applied force,is closer to TMIF than in the case of FIG. 13.

The arrangement of FIG. 13-FIG. 14 may be implemented in many differentways as further explained herein for improving installation and reducingrisk of fracture.

FIG. 15 illustrates a set of parameters and relationships for a forcesensing system 1500 including a generalized FR curve 1505 visualizingvarious applicable forces implicated in operation of the tool in FIG. 13and FIG. 14. Curve 1505 includes TMIF vs displacement of the implant atthe installation site. Early, a small change of TMIF can result is arelatively large change in displacement. However, near the magic spot,the curve starts to transition where the implant is close to beingseated and increases in TMIF may result in little displacement change.And as TMIF increases, the risk of fracture increases.

In FIG. 15, a particular state is illustrated by “X” a point 1510 oncurve 1505. A particular constant value of TMIF 1515 is applied to thesystem and prosthesis P moves along curve 1505. A measured Impact Force(mIF) 1520 approaches the value of TMIF 1515 as prosthesis P approachespoint 1510. A resultant curve 1525 illustrates a difference between TMIF1515 and mIF 1520. As prosthesis P approaches point 1510, resultantcurve 1525 provides a valuable, previously unavailable quantitativeindication of how prosthesis P was responding to applied forces. It maybe that the procedure stops at point 1510, or a new, larger value forTMIF is chosen to move prosthesis P along curve 1505. System 1500provides the surgeon with knowledge of where on curve 1505 theprosthesis P resides and provides an indication of a risk of fractureversus improving seating of prosthesis P. By monitoring resultant curve1525 in some form, system 1300 understands whether prosthesis is movingor has become seated. Each of these pieces of information is useful tosystem 1500 and/or the surgeon until completion of the process.

FIG. 16-FIG. 21 illustrate a first specific implementation of the systemand method of FIG. 13-FIG. 15, FIG. 16 illustrates a representative plot1600 of insertion force for a cup during installation. As prosthesis Pis being installed by a system, device, process, or tool, each incrementof the active installation will have an applicable minimum impact toovercome resistive (e.g., static friction) forces. The impact forcerequired increases as the insertion depth of the cup increases due tolarger normal forces acting on the cup/bone interface (see FIG. 16).There is a tension between seating and increased force though, as largerimpact forces raise the risk of fracture of surrounding bone. The goalof the surgeon is to reach a sufficient insertion depth to generateacceptable cup stability (e.g., pull-out resistance), while minimizingforces imparted to the acetabulum during the process. The process doesnot want to terminate early as the prosthesis may too easily be removedand the process doesn't want to continue too long until the bonefractures. This area is believed to be in the beginning of thenon-linear regime in the plot of FIG. 16, as higher forces begin to havea smaller incremental benefit to cup insertion (i.e. smaller incrementalinsertion depth with larger forces).

FIG. 17 illustrates a first particular embodiment of a BMDX forcesensing tool 1700. Tool 1700 allows indirect measurement of a rate ofinsertion of an acetabular cup and may be used to control the impactforce being delivered to the cup based upon control signals and the useof features of FIG. 16. Tool 1700 may include an actuator 1705, a shaft1710, and a force sensor 1715. One representative method for forcemeasurement/response would employ such a tool 1700. Similar to theimpaction rod currently used by surgeons, tool 1700 would couple to anacetabular cup (prosthesis P) using an appropriate thread at the distalend of shaft 1710. Actuator 1705 would couple to a proximal end of shaft1710, and create controlled impacts that would be applied to shaft 1710and connected cup P. The magnitude of the impact(s) would be controlledby the surgeon through a system control 1720, such as a dial or otherinput mechanism on the device, or directly by the instrument's software.System control 1720 may include a microcontroller 1725 in two-waycommunication with a user interface 1730 and receiving inputs from asignal conditioner 1735 receiving data from force sensor 1715.Controller 1725 is coupled to actuator 1705 to set a desired impactvalue.

Force sensor 1715 may be mounted between the shaft 1710 and acetabularcup P. Sensor 1715 would be of a high enough sampling rate to capturethe peak force generated during an actuator impact. It is known that formultiple impacts of a given energy, the resulting forces increase as theincremental cup insertion distance decreases, see, for example, FIG. 18.FIG. 18 illustrates a graph including results of a drop test over timewhich simulate use of tool 1700 installing cup P into bone.

This change in force given the same impact energy may be a result of thefrictional forces between cup P and surrounding bone of the installationsite. For the plot of FIG. 18, the initial impact has a slowdeceleration of the cup due to its relatively large displacement,resulting in a low force measurement. The displacement decreases forsubsequent impacts due to the increasing frictional forces between thecup and bone, which results in faster deceleration of the cup (the cupis decelerating from the same initial velocity over a shorter distance).This results in an increase in force measurement for each impact. Themaximum force for a given impact energy will be when the cup P can nolonger overcome, responsive to a given impact force from the actuatingsystem, the resistive (e.g., static friction) forces from thesurrounding bone. This results in a “plateau”, where any subsequentimpact will not change either the insertion of cup Por the forcemeasured.

In some embodiments, this relationship may be used to “walk up” theinsertion force plot illustrated in FIG. 16, allowing tool 1700 to findthe “plateau” of larger and larger impact energies. By increasing theenergy linearly, the relationship between measured impact force and cupinsertion illustrated in FIG. 18 should hold until the system reachesthe non-linear insertion force regime of FIG. 16. When the non-linearregime is reached, a small linear increase in impact energy will notovercome the higher static forces needed to continue to insert the cup.This will result in an almost immediate steady state for the measuredimpact force (mIF of a force application X is about the same as MIF of aforce application X+1). A visual representation of the measured impactforce as the impact energy is increased is illustrated in FIG. 19. FIG.19 illustrates a graph of measured impact force as impact energy isincreased. Five impact energy levels are shown, with the last twoincreases in energy resulting in the cup entering the non-linear portionof the insertion force plot illustrated in FIG. 16.

A procedure for automated impact control/force measurement may include:a) Begin impacts with a static, low energy; b) Record the measuredimpact force (MIF); c) continue striking until the difference inmeasured impact force approaches zero (dMIF=>0), inferring that the cupis no longer displacing; d) increase the energy of the impacts by aknown, relatively small amount; and e) repeat striking until plateau andincreasing energy in a linear fashion until an increase in energy doesnot result in the relationship shown in FIG. 18. Instead, an increase inenergy results in a “step function” in recorded forces, with animmediate steady state. The user could be notified of each increase inenergy, allowing a decision by the surgeon to increase the resultingimpact force.

FIG. 20 illustrates a discrete impact control and measurement process2000. Process 2000 includes step 2005-step 2045. Step 2005 (start)initializes process 2000. Process 2000 advances to a step 2010 toinitiate the actuator to impart a known force application with energy Xjoules. After step 2010, process 2000 advances to step 2015 to measureimpact force (MIF). After step 2015, process 2000 tests whether therehave been a sufficient number of force applications to properlyevaluate/measure a delta MIF (dMIF) between an initial value and acurrent value. When the test at step 2020 is negative, process 2000returns to step 2010 to generate another force application event.Process 2000 continues with steps 2010-2020 until the test at step 2020is affirmative, at which point process 2000 advances to a test at step2025. Step 2025 tests whether the evaluated dMIF is approaching within apredetermined threshold of zero (that is, MIF(N)−MIF(N−1)=>0 within adesired threshold. When the test at step 2025 is negative, process 2000returns to step 2010 for produce another force application event andprocess 2000 repeats steps 2010-2025 until the test at step 2025 isaffirmative.

When affirmative, process 2000 advances to a step 2030 and includes auser feedback event to inform a surgeon/observer that the prosthesis isno longer inserting at a given TMIF value. After step 2030, process 2000may include a test at step 2035 as to whether the user desires toincrease the TMIF. Some implementations may not include this test (andeither automatically continue until a termination event or the systemstops automatically).

In the test at step 2035, the user may choose to have the energy appliedfrom the actuator increased. Process 2000 includes a step 2040 after anaffirmative result of the test at step 2035 which increases the currentenergy applied by the actuator an additional Y joule. After the changeof energy at step 2040, process 2000 returns to repeat steps 2010-2035until the test at step 2035 is negative. At which point, process 2000advances to an end step 2045 which may include any post-installationprocessing.

Once the non-linear regime discussed in FIG. 16 is reached, theprobability of fracture increases. This is due to the acetabular cupnearing its full insertion depth, with limited incremental displacementfrom additional blows. This results in larger impact forces that aretransmitted to the surrounding bone. Tool 1700 is able to detect whenthis regime is reached using process 2000, and could generate an alertthrough the user interface. The implementation of an alert could beperformed in a number of different ways. One way would be a warninglight and/or tone that would activate when a “step function” increase inmeasured impact force is detected. More advanced implementations arepossible, with the system indicating the increasing probability offracture as impact energy is increased once a “step function” increasein measured impact force is detected. The increasing risk of fracturecould be shown through an LED bar that would illuminate additionallights to correspond to the relative risk, or by computing anddisplaying a fracture probability directly on the user interface. Itshould be noted that the cup may not fully seated when the systemgenerates the aforementioned alert. This could be due to cup alignmentissues, incorrect bone preparation, or incorrect cup sizing, among othercauses. In these instances, the system would generate an alert beforethe cup is fully inserted, allowing the surgeon to stop and determinethe cause of the alert. This may be an additional benefit, allowingdetection of an insertion issue before larger impact forces are used. Aflowchart for one form of warning implementation is illustrated in FIG.21.

FIG. 21 illustrates a warning process 2100. Process 2100 includes a step2105-step 2140. Step 2105 (start) initializes process 2100. Process 2100advances to a step 2110 to initiate the actuator to impart a known forceapplication with energy X joules. After step 2110, process 2100 advancesto step 2115 to measure impact force (MIF). After step 2115, process2100 tests whether there have been a sufficient number of forceapplications to properly evaluate/measure a delta MIF (dMIF) between aninitial value and a current value. When the test at step 2120 isnegative, process 2100 returns to step 2110 to generate another forceapplication event. Process 2100 continues with steps 2110-2120 until thetest at step 2120 is affirmative, at which point process 2100 advancesto a test at step 2125. Step 2125 tests whether the evaluated dMIF isapproaching within a predetermined threshold of zero (that is,MIF(N)−MIF(N−1)=>0 within a desired threshold. When the test at step2125 is negative, process 2100 returns to step 2110 for produce anotherforce application event and process 2100 repeats steps 2110-2125 untilthe test at step 2125 is affirmative.

When affirmative, process 2100 advances to a step 2130 and includes awarning test event to test whether a first and a last MIF are withinmeasurement error (MIF(0)=MIF(N)?) When the test at step 2130 isaffirmative, a warning may be issued. When the test at step 2130 isnegative, no warning is issued. There are similarities with process 2000and process 2100 and some embodiments may combine them.

Improved performance may arise when the device is in the same statebefore each impact, in that the force applied by the user to the deviceis relatively consistent. Varying the user's input may influence themeasured impact force for a strike, resulting in erroneous resistancecurve modeling by the device. In order to minimize the occurrence, thedevice could actively monitor the force sensor between impacts, lookingfor a static load before within an acceptable value range. The systemcould also use the static load measurements directly before a strike asthe impact's reference point, allowing relative measurements that reducethe effect of user variation. Even with this step, it is expected thatfiltering and statistical analysis will need to be performed in order tominimize signal noise.

FIG. 22-FIG. 27 illustrate a second specific implementation of thesystem and method of FIG. 13-FIG. 15; FIG. 22 illustrates a basic forcesensor system 2200 for controlled insertion. System 2200 includes ahandle 2205, a first force sensor 2210, a shock absorber 2215, a motor2220, a second force sensor 2225, and impact rod 2230, and a processingunit 2235. A purpose of system 2200 is to use force measurements andestimates to provide cup settlement feedback. A basic configuration ofthe hardware involved in system 2200 is illustrated in FIG. 22.Important sensors include: Preload sensor 2210, motor current sensorlocated in PPU 2235; and impaction sensor 2225. Instrumentation ofsystem 2200 either measures or estimates variables illustrated in FIG.23. FIG. 23 illustrates an FR curve including TmIF and mIF as functionsof displacement. FIG. 24 illustrates a generic force sensor tool toaccess variables of interest in FIG. 23. System 2400, correspondinggenerally to system 1300 includes a force sensor 2405 (measuring F), adamping mechanism 2410, a current sensor (TmIF estimation and Actuator)function 2415, a vibrating/impacting interface 2420, and a force sensor2425 (measuring mIF).

The relationship among the three curves in FIG. 23 are able to determinethe cup/cavity settlement behavior. mIF can be directly measured bysystem 2200 as described herein. For example, impaction sensor 2225 maybe a force sensor placed in the impacting rod 2230. The impacting rod2230 receives and transmits impacts directly to the cup. This sameimpaction force input is sensed by sensor 2225.

TmIF is composed by both preload and actuator force. The preload ismeasured directly by the force sensor 2210. The actuator force can beestimated by means of current sensing (motor 2220 and PPU 2235) as thetorque/force generated by the motor can be related to its electriccurrent.] C. L. Chu, M. C. Tsai, H. Y. Chen, “Torque control ofbrushless dc motors applied to electric vehicles,” in IEEE InternationalElectric Machines and Drives Conference, 2001, pp. 82-87.

Motor 2020 is connected to PPU 2035 where the current sensor isinstalled. All measurements shall be properly filtered and handled inreal-time before any advanced processing takes place. Both low level andadvanced real-time processing are executed in PPU 2035 for each sensor.Sensor 2025 needs less processing since this is the direct measurementof mIF. TmIF needs more processing since it is composed by directmeasurement of sensor 2010 and estimated force provided by motor 2020.Force estimation is basically data fusion of brushless DC motor currentmeasurements with its electromechanical mathematical model consideringmechanism interactions.

Once mIF and TmIF are internally available (to the PPU), the frequencyof the actuating mechanism can be changed as a function of thesevariables. This allows the tool to track the optimal region (theB-Cloud) of the FR-Curve. It is important to note that mIF steady statevalue depends on current TmIF. In other words, the B-Cloud can besuitably tracked by the combination of both TmIF and mIF as described inthe flowchart of FIG. 25.

FIG. 25 illustrates a B-cloud tracking process 2500 using TmIF and MIFmeasurements. Process 2500 includes step 2505-step 2545. Step 2505, astart step, initiates process 2500. After start 2505, process 2500includes a test step 2510 to determine whether TmIF=mIF. When negative,process 2500 performs a controlled action step 2515 and then returns tostep 2510. Process 2500 repeats steps 2510-2515 until the test at step2510 is affirmative, at which point process 2500 performs a test step2520 to determine whether the B-cloud is achieved. When the test at step2520 is negative, process 2500 performs a test step 2525 to determinewhether to change the preload. When the test at step 2525 is negative,process 2500 performs a controlled action step 2530 and then branches toAA—to the test at step 2520.

When the test at step 2525 is affirmative, process 2500 queries thesurgeon at step 2535 as to changing the preload. In response to surgeonconsultation step 2535, process 2500 performs controlled action step2530. Process 2500 repeats steps 2520-2535 until the test at step 2520is affirmative. When affirmative, process 2500 performs a stop insertionstep 2540 and may either ask surgeon at step 2530 and/or concludeprocess 2500 by performing an end step 2545.

Process 2500 begins when the cup is preloaded against the cavity. It maybe triggered by force threshold or button press. Current TmIF and mIFare constantly compared and regulated to be equal according to aninternal control system when they are not able to converge easily. Thecontrol system is detailed in FIG. 26. FIG. 26 illustrates a controlsystem 2600 for the “controlled action” referenced in FIG. 25.

Control system 2600 includes a set of processing blocks, real objects,computed signals and raw measurement and computed signals selectivelyresponsive to input force and input frequency commands. System 2600includes a feedback block 2605, a Bcloud regulator block 2610, a controlselector 2615, a device/cavity/cup interaction assessment 2620, an FRcurve estimator 2625, a feedback block 2630, and a performance pursuitblock 2635.

Feedback block 2605 compares TMIF against an output (input force commandand mIF) of block 2620. When/If there is an Input Force error at block2605, B cloud Regulator provides a first input frequency command f1 inresponse to the IF error. Feedback block 2630 compares a maximumfeasible gain against a cup/cavity gain estimate from FR estimator 2625.When/if there is a gain error, performance pursuit 2635 takes this gainerror and produces a second input frequency command. Control selector2615 accepts both input frequency commands and selects one and providesit to the device/cavity/cup interaction 2620. Interaction 2620 producesinput force command and mIF to FR estimator 2625, to selector 2615, andto feedback block 2605.

As the achievement of the B-Cloud is an objective, it is also constantlyverified if it was achieved. However, the achievement of the B-Cloud isconstrained to the value of the force source measured by TmIF. When theB-Cloud is not achieved, it is evaluated if there is need of pre-loadincrease or not (i.e. the actuator alone would be able to increaseTmIF). In case of additional pre-load needed, the device asks thesurgeon to increase the pre-load. The control system keeps running tomake mIF track TmIF in an optimized way. The insertion stopsautomatically when the B-Cloud is achieved for the first time. Areference value inside the B-Cloud can be adjusted by the surgeon if sherealizes based on its visual feedback that additional or less insertionforce is necessary.

There are possible exceptions related to abnormal or unexpectedcup/cavity behavior. As a cup/cavity which needs too much pre-load ormuch more force than some actuators are able to achieve. For this reasonthe “B-Cloud regulation” block 2610 in FIG. 26 may be implemented in twodistinct ways: a BMD3 device alone (curve 2705 in FIG. 27—mIF strongBMD3); or hybrid BMD3/BMD4 devices combined (curve 2710 with “weak” mIFBMD3 switched to BMD4-hybrid or discrete devices).

FIG. 27 illustrates possible B-cloud regulation strategies. A value onthe B-Cloud is taken as reference for the B-Cloud regulator, this valueis expressed by the dashed line in 27. In the case of a BMD3 able toperform the job alone, it can be achieved smoothly. In the case thatBMD3 does not have sufficient power to accomplish the task, it switchesto BMD4 which provides incremental impacts proportional to thedifference between mIF and TmIF. Progressive BMD4 impacts change itsamplitude following K_(BMD4)(m_(IF)−T_(mIF)), while K_(BMD) is aparameter which has to be determined experimentally.

Estimation of the force provided by the motor

A reliable and feasible way to determine the amount of force madeavailable by the actuator is by means of electrical current measurement.The accuracy and sizes involved in our application would make difficultthe installation of force/torque sensors for motors and piezotransducers, which are the basic types of actuators used in BMD3 andBMD4 devices. However, electrical current drawn by these actuators isrelated to the force produced by them. In other words, the forceproduced can be understood as a function of the electrical current. Thisidea is largely in engineering. Our proposed solution would make use ofestimators (e.g. Kalman filter) which relate the mathematical model ofthe electromechanical actuator fused with measured values of theelectrical current to provide the force output generated in real-time bythe actuator

FIG. 28 illustrates a generalized BMD 2800 including real-time invasivesense measurement. BMD 2800 includes one or moremicro-electro-mechanical systems (MEMS) 2805 to measure real-timeinvasive sense measurement for BMD 2800. MEMS 2805 are secured to BMD2800, such as by for example, an attachment or other coupling to ahandle 2810 of BMD 2800. As illustrated, BMD 2800 includes an acetabularcup C for installation, though other systems may be used for differentprosthetics.

During a procedure, MEMS 2805 provides real-time parametric evaluationof relevant information that may be needed or desired by an operator ofhandle 2810. For example, an orientation and seatedness of cup C may beevaluated in real-time to allow the operator to suspend operation when adesired orientation and/or seatedness has been achieved. MEMS 2805 mayevaluate orientation, displacement depth, seatedness, using a range ofpotential sensing systems, including force, acceleration, vibration,acoustics, and other information. Just as an interaction between cup Cand an installation site may produce an FR curve as described herein,various interactions of BMD 2800 or one or more components of BMD 2800(e.g., cup C) with the installation site may produce characteristicprofiles or “prints” that change during the real-time operation.Monitoring these parametric prints in true real-time may provide theoperator with helpful information that is not available with a series ofpre-process measurement and post-process measurement.

The force parameter has been described herein. Other parameters ofacceleration, vibration, acoustic, and the like information may providehelpful information as well by including appropriate sensing structuresfor acceleration, vibration, acoustic, and the like. In the case of aninstallation depth of an acetabular cup, these parameters may help theoperator to identify and differentiate between the three zones: toolittle seatedness zone, sweet zone, and fracture-risk zone. Thespecifics by which these zones are detected and identified are likely tobe different, however.

BMD 2800, by appropriate selection of multiple sensing systems in MEMS2805, may improve performance by providing a logical product ofdifferent parametric evaluations. That is, while any single parameter offorce, acceleration, vibration, acoustic, or the like may offer improvedperformance, having multiple different sensors all operating in truereal-time to cross/double check can offer improved performance.

In some cases, a system may not identify that the prosthesis is in thesweet zone unless multiple parametric systems concur. In other cases, itmay be that a first to detect a fracture-risk zone may result insuspension or termination of the installation process. Or that allsystems must indicate adequate seatedness before stopping (possiblyadding a further condition of providing no fracture risk detection).

Even without automatic detection of these zones, the combinedinformation may useful to the operator in evaluating how to proceed withthe installation to help maximize the desired orientation and seatednesswithout unnecessarily risking fracture.

Other procedures besides cup installation (e.g., installing a differenttype of prosthesis), other processes other than prosthesis installation(e.g., assembling a modular prosthesis), and other invasive operations(e.g., bone preparation), and other medical interventions that do notrelate to prosthesis preparation, installation, and assembly may allbenefit from providing true real-time analysis and feedback.

Feedback from a MEMS sensing system may be accomplished by one or moreof a display or indicator on or integrated with the device, and/or anassociated module in communication with the MEMS sensing system/display,a robot or navigation system in communication with the MEMS sensingsystem and/or an associated module.

The system and methods above have been described in general terms as anaid to understanding details of preferred embodiments of the presentinvention. In the description herein, numerous specific details areprovided, such as examples of components and/or methods, to provide athorough understanding of embodiments of the present invention. Somefeatures and benefits of the present invention are realized in suchmodes and are not required in every case. One skilled in the relevantart will recognize, however, that an embodiment of the invention can bepracticed without one or more of the specific details, or with otherapparatus, systems, assemblies, methods, components, materials, parts,and/or the like. In other instances, well-known structures, materials,or operations are not specifically shown or described in detail to avoidobscuring aspects of embodiments of the present invention.

Reference throughout this specification to “one embodiment”, “anembodiment”, or “a specific embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention and notnecessarily in all embodiments. Thus, respective appearances of thephrases “in one embodiment”, “in an embodiment”, or “in a specificembodiment” in various places throughout this specification are notnecessarily referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics of any specificembodiment of the present invention may be combined in any suitablemanner with one or more other embodiments. It is to be understood thatother variations and modifications of the embodiments of the presentinvention described and illustrated herein are possible in light of theteachings herein and are to be considered as part of the spirit andscope of the present invention.

It will also be appreciated that one or more of the elements depicted inthe drawings/figures can also be implemented in a more separated orintegrated manner, or even removed or rendered as inoperable in certaincases, as is useful in accordance with a particular application.

Additionally, any signal arrows in the drawings/Figures should beconsidered only as exemplary, and not limiting, unless otherwisespecifically noted. Combinations of components or steps will also beconsidered as being noted, where terminology is foreseen as renderingthe ability to separate or combine is unclear.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the Abstract, is not intendedto be exhaustive or to limit the invention to the precise formsdisclosed herein. While specific embodiments of, and examples for, theinvention are described herein for illustrative purposes only, variousequivalent modifications are possible within the spirit and scope of thepresent invention, as those skilled in the relevant art will recognizeand appreciate. As indicated, these modifications may be made to thepresent invention in light of the foregoing description of illustratedembodiments of the present invention and are to be included within thespirit and scope of the present invention.

Thus, while the present invention has been described herein withreference to particular embodiments thereof, a latitude of modification,various changes and substitutions are intended in the foregoingdisclosures, and it will be appreciated that in some instances somefeatures of embodiments of the invention will be employed without acorresponding use of other features without departing from the scope andspirit of the invention as set forth. Therefore, many modifications maybe made to adapt a particular situation or material to the essentialscope and spirit of the present invention. It is intended that theinvention not be limited to the particular terms used in followingclaims and/or to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include any and all embodiments and equivalents falling within thescope of the appended claims. Thus, the scope of the invention is to bedetermined solely by the appended claims.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. An apparatus for insertion of a prosthesis intoa cavity in a portion of bone, the prosthesis relatively oversized withrespect to the cavity, comprising: an insertion device providing aninsertion agency to the prosthesis, said insertion agency operating overa period including an initial prosthesis insertion act with saidinsertion device to a subsequent prosthesis insertion act with saidinsertion device; and a sensing system physically coupled to saidinsertion device configured to provide a parametric evaluation of anextractive force of an interface between the prosthesis and the cavityduring said period.
 2. The apparatus of claim 1 wherein said insertiondevice includes a prosthesis insertion device and wherein saidparametric evaluation includes a quality of a seatedness and a metric ofa fracture-risk of the portion of bone; and wherein said quality ofseatedness includes said extractive force of said interface.
 3. Theapparatus of claim 1 wherein an applied force having a first magnitudeis applied to said insertion device for inserting the prosthesis intothe cavity, further comprising: a device sensor configured to measure amagnitude of a measured impact force within said insertion deviceresponsive to an application of said applied force to said medicaldevice.
 4. The apparatus of claim 3 wherein said first magnitude of saidapplied force includes a predetermined applied force having apredetermined first magnitude.
 5. The apparatus of claim 4 furthercomprising an applied force sensor configured to measure said firstmagnitude of said applied force.
 6. The apparatus of claim 1 whereinsaid insertion agency includes a vibratory insertion force.
 7. Theapparatus of claim 1 wherein said insertion agency includes a periodiccontrolled impaction insertion force.
 8. The apparatus of claim 1further including a robot and wherein said insertion agency includes acontinuous insertion force provided by said robot.
 9. The apparatus ofclaim 1 wherein the prosthesis includes an acetabular cup.
 10. Theapparatus of claim 1 wherein said parametric evaluation of saidextractive force includes a response of the prosthesis within the cavityto said insertion agency.
 11. The apparatus of claim 10 wherein saidinsertion agency includes an applied force directed to the prosthesisand wherein said response includes a force response of the prosthesiswithin the cavity.
 12. An apparatus for an insertion of a prosthesisinto a cavity having a cavity perimeter in a portion of bone, theprosthesis having a prosthesis perimeter relatively oversized withrespect to the cavity perimeter, comprising: means for applying aninsertion agency to the prosthesis, said insertion agency directing theinsertion of the prosthesis into the cavity; and means, coupled to saidmeans for applying said insertion agency and responsive to saidinsertion agency, for determining a parametric evaluation of anextractive force of an interface between the prosthesis and the cavityduring an application of said insertion agency to the prosthesis. 13.The apparatus of claim 12 further comprising: means, coupled to saidmeans for determining said parametric evaluation and responsive to saidparametric evaluation during said application of said insertion agencyto the prosthesis, for assessing a quality of seatedness of theprosthesis within the cavity.